May 2015- Physics Paper 1 and Paper 2

[Sofia.]

Hm, I just figured since we had the velocity and the wave length that we could do v/lambda to find the frequency of wave B, and that would match the frequency of the minima since they only happen once a period. 

 

I study astrophysics and particles, you?

[Sofia.]

 

 

@Ossih, although I didn't do the exam, I think I might have spotted 2 mistakes of yours.

 

 

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

 

I think the assumption should be the elasticity of the collisions (that is in agreement with wikipedia).

Although it's true that temperature is proportional to the average kinetic energy of the molecules, but I don't think that it was an assumption; it was actually a mathematical consequence of the kinetic model. Wikipedia only says that:

• The average kinetic energy of the gas particles depends only on the absolute temperature of the system

This means that kinetic energy has a relationship with the temperature, but this assumption isn't very clear on what type of relationship it is. It's only when you work out the mathematics that you find the temperature to be proportional to the kinetic energy.

 

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative

 

I would agree with Hassan76 for this one, though I may be wrong. It's true that the same number of electrons are ejected due to the same intensity of the light that was used. But increasing the frequency of the photons means that you've increased the kinetic energy of the emitted electrons. This will cause the electrons to move faster (since KE is proportional to the speed). Here, you need to realize that current is the measure of charge per unit time. The increase in speed will increase the number of charge per unit time, thus the current must increase.

So the chain of reasoning is as follow:

 

Higher frequency --> larger KE --> electrons gaining speed --> more photocurrent --> more negative stopping potential

 

And damn, it's crazy to see how you guys remembered all that stuff!!! Good luck with the rest of the exams

 

Thanks Vioh! I think you may be right for the temperature one. But this site http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phases_of_Matter/Gases/Kinetic_Theory_of_Gases/Kinetic_Theory_of_Gases states both as assumptions of the Kinetic theory so I really don't know. My book only states elastic though, so maybe that's what it is. Oh well, we'll find out soon enough ahha

 

However, for the photocurrent one, I'm sure, because it said that the number of photons per second is the same, (it doesn't say the same intensity of light, that would give a different result) implying that the number of electrons per second is the same (assuming that we're above threshold frequency). Because of that photocurrent must stay the same. 

 

If it were same intensity of light, then I agree, the photocurrent would change

 

I just hope I get a 7. I think it was a pretty think-out-of-the-box paper so a boundary for a 7 will be 32-34ish, so I hope I'll be fine

Guys concerning this question, 1- it is low pressure and high temperature, 2- these are not assumptions they are facts otherwise it will be a real gas

 

 

No, low pressure and high temperature is simply when a real gas acts the most as an ideal gas - elasticity is an assumption. 

[Hassan76]

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

2.For the projectile, it was fired above the horizontal.

3.For the equipotentials, yeah, same mass and same charges.

4. The electron accelerating thing, damn you're right haha I did that one wrong.

5. Yeah, constant net force and fixed mass.

6. Yeah the first question, the ratio of the orders of magnitude was 3.

7. The girl's gain in energy is 600J yup

8. Entropy of the universe increases, yea

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

11. I don't remember the emissivity question hm.

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

13. Resolution was to replace with a violet light yea

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

15. Yeah the wave velocity to the right was A.

16. U tube was D, the damped one.

17. Hm, for the electric field strength one, I chose A, the one furthest from both.

18. Yeah its VI

19. Yes, artificial transmutations was C.

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

21. For the water and paraffin, it was 60º yup

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

23. For evidence of nuclear energy levels, its alpha and gamma yup

I can't remember the power of the wave and de Broglie wavelength questions.

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

25. For resistance the ratio was 8:1 yup

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

Btw holy crap haha you have a great memory.

Others that I remember

31. Albedo was water < desert < snow

32. The last question (about the potential difference on a pixel) was nNe/C

33. The 2/3rd question (the one with the graph), she is constantly accelerating

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

35. The renewable energy source was 10% :/ I put 30%

36. The units of capacitance was the one with s^4 (A I think).

I can't remember the remaining 4 haha, what were they?

Above the horizontal? Do you mean vertically upwards? Edited May 10, 2015 by Hassan76

[Hassan76]

Hm, I just figured since we had the velocity and the wave length that we could do v/lambda to find the frequency of wave B, and that would match the frequency of the minima since they only happen once a period. 

 

I study astrophysics and particles, you?

But do you think this answer gets the 3 marks , you know if it was 1 mark I would use v over lambda... I study medical and astro

[Sofia.]

 

Hm, I just figured since we had the velocity and the wave length that we could do v/lambda to find the frequency of wave B, and that would match the frequency of the minima since they only happen once a period. 

 

I study astrophysics and particles, you?

But do you think this answer gets the 3 marks , you know if it was 1 mark I would use v over lambda... I study medical and astro

 

 

Wasn't it two marks? I figured one was for the calculation of the frequency of B, another for realizing it's the same as that of the minima, but then again I wasn't totally sure I did the right thing either. 

[Sofia.]

 

 

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

2.For the projectile, it was fired above the horizontal.

3.For the equipotentials, yeah, same mass and same charges.

4. The electron accelerating thing, damn you're right haha I did that one wrong.

5. Yeah, constant net force and fixed mass.

6. Yeah the first question, the ratio of the orders of magnitude was 3.

7. The girl's gain in energy is 600J yup

8. Entropy of the universe increases, yea

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

11. I don't remember the emissivity question hm.

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

13. Resolution was to replace with a violet light yea

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

15. Yeah the wave velocity to the right was A.

16. U tube was D, the damped one.

17. Hm, for the electric field strength one, I chose A, the one furthest from both.

18. Yeah its VI

19. Yes, artificial transmutations was C.

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

21. For the water and paraffin, it was 60º yup

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

23. For evidence of nuclear energy levels, its alpha and gamma yup

I can't remember the power of the wave and de Broglie wavelength questions.

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

25. For resistance the ratio was 8:1 yup

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

Btw holy crap haha you have a great memory.

Others that I remember

31. Albedo was water < desert < snow

32. The last question (about the potential difference on a pixel) was nNe/C

33. The 2/3rd question (the one with the graph), she is constantly accelerating

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

35. The renewable energy source was 10% :/ I put 30%

36. The units of capacitance was the one with s^4 (A I think).

I can't remember the remaining 4 haha, what were they?

Above the horizontal? Do you mean vertically upwards?

 

 

Vertically upwards would mean that it had zero velocity in the horizontal direction, i.e. you just throw it straight upwards. It had to be above the horizontal, i.e. upwards but also forwards, because the horizontal velocity was not zero, and the vertical was initially positive (indicating upward movement) and then negative, when it was moving downwards. 

[Hassan76]

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

 

 

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

 

2.For the projectile, it was fired above the horizontal.

 

3.For the equipotentials, yeah, same mass and same charges. 

 

4. The electron accelerating thing, damn you're right haha I did that one wrong.

 

5. Yeah, constant net force and fixed mass.

 

6. Yeah the first question, the ratio of the orders of magnitude was 3.

 

7. The girl's gain in energy is 600J yup

 

8. Entropy of the universe increases, yea

 

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

 

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

 

11. I don't remember the emissivity question hm.

 

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

 

13. Resolution was to replace with a violet light yea

 

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

 

15. Yeah the wave velocity to the right was A.

 

16. U tube was D, the damped one. 

 

17. Hm, for the electric field strength one, I chose A, the one furthest from both. 

 

18. Yeah its VI

 

19. Yes, artificial transmutations was C.

 

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

 

21. For the water and paraffin, it was 60º yup

 

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

 

23. For evidence of nuclear energy levels, its alpha and gamma yup

 

I can't remember the power of the wave and de Broglie wavelength questions.

 

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

 

25. For resistance the ratio was 8:1 yup

 

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

 

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

 

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

 

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

 

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

 

Btw holy crap haha you have a great memory.

 

Others that I remember

 

31. Albedo was water < desert < snow

 

32. The last question (about the potential difference on a pixel) was nNe/C

 

33. The 2/3rd question (the one with the graph), she is constantly accelerating

 

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

 

35. The renewable energy source was 10% :/ I put 30%

 

36. The units of capacitance was the one with s^4 (A I think).

 

I can't remember the remaining 4 haha, what were they?

Look Ossih , realy I appreciate that you are grated by skills I don't have and I was proud to ask you, I wish that we all get 7s and the grades we want, but for the electric field strength it is b, closer to 20, since thé ratio of the distances is like 1/4, ratio of charges squared, since e f strength is related to square of distance, like when you have an athlete and some one who does not have good fitness, if you want both to get tired the same way, the athlete has to run more, right? ,

For the mass spectrometer it was one of the straight forward question, same q, double m half v, the doubling of mass will cancel the halving in v, cos they are both in the numerator, but changing q would make a further change, right ?

For the assumptions I don't remember at all that they mentioned temperature which makes me doubt that you may be right, but remember the rubric invites us to chose the best answer and you could some assumptions that won't significantly affect the physics, this is mentioned in the subject report, you know for example, when in p1 they ask you wht is b energy, we would all chose energy.... To separate the nucleus from nucleons, but the answer is to form a nucleus from its nucleons, Do you remember the question about which process will increase the entropy of the local surroundings? In m14 hpm tz2, the answer was isothermal expansion and it should be compression according to Ib past papers not only my understanding, wht do you think

The remaining 4 questions are the new wavelenth when the voltage is quadrupled, the 4 bits possible combinations which I oppose because it is simply about memorizing that it is 2 to the power of n, and I did not know that it is in our s guide, I chose 8 as I thought that zeros in the beginning cannot exist otherwise no difference between , 3 , 4, 5 bits number because both 001 and 01 gives the same decimal number right, but they are 3 and 2 bits, My opposition also is because as you said Ossih the questions demanded a lot of thinking, and this makes me like what I am doing , but that digital technology topic, what are the physics in it, and the energy topic, they are very easy topics but requires a lot of memorizing,

And the other 2 remaining is the question after that of the e field strength of 0 which asked when the electron goes out of the field what happens to its velocity and acceleration, that it is v is increasing, a is decreasing, do you remember it is related to the question in q9 about why the average speed of the electron does not increase, and the last one is the waves question about the rope, and the reflection and inversion,my he wave pulse, Btw I struggled to remember half of those question on Friday even with the help of some friends, but once you remember one you get the others.

What options do you take Ossih?

[Hassan76]

Hm, I just figured since we had the velocity and the wave length that we could do v/lambda to find the frequency of wave B, and that would match the frequency of the minima since they only happen once a period. 

 

I study astrophysics and particles, you?

But do you think this answer gets the 3 marks , you know if it was 1 mark I would use v over lambda... I study medical and astro

 

Wasn't it two marks? I figured one was for the calculation of the frequency of B, another for realizing it's the same as that of the minima, but then again I wasn't totally sure I did the right thing either.

3 Sofia, and this what made me doubt my answer, maybe one mark required a statement about path difference or something

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

YA Inagree with you, so what was the answer?

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

2.For the projectile, it was fired above the horizontal.

3.For the equipotentials, yeah, same mass and same charges.

4. The electron accelerating thing, damn you're right haha I did that one wrong.

5. Yeah, constant net force and fixed mass.

6. Yeah the first question, the ratio of the orders of magnitude was 3.

7. The girl's gain in energy is 600J yup

8. Entropy of the universe increases, yea

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

11. I don't remember the emissivity question hm.

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

13. Resolution was to replace with a violet light yea

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

15. Yeah the wave velocity to the right was A.

16. U tube was D, the damped one.

17. Hm, for the electric field strength one, I chose A, the one furthest from both.

18. Yeah its VI

19. Yes, artificial transmutations was C.

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

21. For the water and paraffin, it was 60º yup

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

23. For evidence of nuclear energy levels, its alpha and gamma yup

I can't remember the power of the wave and de Broglie wavelength questions.

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

25. For resistance the ratio was 8:1 yup

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

Btw holy crap haha you have a great memory.

Others that I remember

31. Albedo was water < desert < snow

32. The last question (about the potential difference on a pixel) was nNe/C

33. The 2/3rd question (the one with the graph), she is constantly accelerating

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

35. The renewable energy source was 10% :/ I put 30%

36. The units of capacitance was the one with s^4 (A I think).

I can't remember the remaining 4 haha, what were they?

Above the horizontal? Do you mean vertically upwards?

 

Vertically upwards would mean that it had zero velocity in the horizontal direction, i.e. you just throw it straight upwards. It had to be above the horizontal, i.e. upwards but also forwards, because the horizontal velocity was not zero, and the vertical was initially positive (indicating upward movement) and then negative, when it was moving downwards.

[Sofia.]

 

 

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

 

 

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

 

2.For the projectile, it was fired above the horizontal.

 

3.For the equipotentials, yeah, same mass and same charges. 

 

4. The electron accelerating thing, damn you're right haha I did that one wrong.

 

5. Yeah, constant net force and fixed mass.

 

6. Yeah the first question, the ratio of the orders of magnitude was 3.

 

7. The girl's gain in energy is 600J yup

 

8. Entropy of the universe increases, yea

 

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

 

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

 

11. I don't remember the emissivity question hm.

 

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

 

13. Resolution was to replace with a violet light yea

 

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

 

15. Yeah the wave velocity to the right was A.

 

16. U tube was D, the damped one. 

 

17. Hm, for the electric field strength one, I chose A, the one furthest from both. 

 

18. Yeah its VI

 

19. Yes, artificial transmutations was C.

 

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

 

21. For the water and paraffin, it was 60º yup

 

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

 

23. For evidence of nuclear energy levels, its alpha and gamma yup

 

I can't remember the power of the wave and de Broglie wavelength questions.

 

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

 

25. For resistance the ratio was 8:1 yup

 

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

 

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

 

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

 

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

 

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

 

Btw holy crap haha you have a great memory.

 

Others that I remember

 

31. Albedo was water < desert < snow

 

32. The last question (about the potential difference on a pixel) was nNe/C

 

33. The 2/3rd question (the one with the graph), she is constantly accelerating

 

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

 

35. The renewable energy source was 10% :/ I put 30%

 

36. The units of capacitance was the one with s^4 (A I think).

 

I can't remember the remaining 4 haha, what were they?

Look Ossih , realy I appreciate that you are grated by skills I don't have and I was proud to ask you, I wish that we all get 7s and the grades we want, but for the electric field strength it is b, closer to 20, since thé ratio of the distances is like 1/4, ratio of charges squared, since e f strength is related to square of distance, like when you have an athlete and some one who does not have good fitness, if you want both to get tired the same way, the athlete has to run more, right? ,

For the mass spectrometer it was one of the straight forward question, same q, double m half v, the doubling of mass will cancel the halving in v, cos they are both in the numerator, but changing q would make a further change, right ?

For the assumptions I don't remember at all that they mentioned temperature which makes me doubt that you may be right, but remember the rubric invites us to chose the best answer and you could some assumptions that won't significantly affect the physics, this is mentioned in the subject report, you know for example, when in p1 they ask you wht is b energy, we would all chose energy.... To separate the nucleus from nucleons, but the answer is to form a nucleus from its nucleons, Do you remember the question about which process will increase the entropy of the local surroundings? In m14 hpm tz2, the answer was isothermal expansion and it should be compression according to Ib past papers not only my understanding, wht do you think

The remaining 4 questions are the new wavelenth when the voltage is quadrupled, the 4 bits possible combinations which I oppose because it is simply about memorizing that it is 2 to the power of n, and I did not know that it is in our s guide, I chose 8 as I thought that zeros in the beginning cannot exist otherwise no difference between , 3 , 4, 5 bits number because both 001 and 01 gives the same decimal number right, but they are 3 and 2 bits, My opposition also is because as you said Ossih the questions demanded a lot of thinking, and this makes me like what I am doing , but that digital technology topic, what are the physics in it, and the energy topic, they are very easy topics but requires a lot of memorizing,

And the other 2 remaining is the question after that of the e field strength of 0 which asked when the electron goes out of the field what happens to its velocity and acceleration, that it is v is increasing, a is decreasing, do you remember it is related to the question in q9 about why the average speed of the electron does not increase, and the last one is the waves question about the rope, and the reflection and inversion,my he wave pulse, Btw I struggled to remember half of those question on Friday even with the help of some friends, but once you remember one you get the others.

What options do you take Ossih?

 

 

Pretty sure you can define binding energy either way. 

Maybe it was one mark for converting mm to m? How did you solve the question, anyway?

[Hassan76]

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

 

 

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

 

2.For the projectile, it was fired above the horizontal.

 

3.For the equipotentials, yeah, same mass and same charges. 

 

4. The electron accelerating thing, damn you're right haha I did that one wrong.

 

5. Yeah, constant net force and fixed mass.

 

6. Yeah the first question, the ratio of the orders of magnitude was 3.

 

7. The girl's gain in energy is 600J yup

 

8. Entropy of the universe increases, yea

 

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

 

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

 

11. I don't remember the emissivity question hm.

 

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

 

13. Resolution was to replace with a violet light yea

 

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

 

15. Yeah the wave velocity to the right was A.

 

16. U tube was D, the damped one. 

 

17. Hm, for the electric field strength one, I chose A, the one furthest from both. 

 

18. Yeah its VI

 

19. Yes, artificial transmutations was C.

 

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

 

21. For the water and paraffin, it was 60º yup

 

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

 

23. For evidence of nuclear energy levels, its alpha and gamma yup

 

I can't remember the power of the wave and de Broglie wavelength questions.

 

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

 

25. For resistance the ratio was 8:1 yup

 

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

 

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

 

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

 

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

 

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

 

Btw holy crap haha you have a great memory.

 

Others that I remember

 

31. Albedo was water < desert < snow

 

32. The last question (about the potential difference on a pixel) was nNe/C

 

33. The 2/3rd question (the one with the graph), she is constantly accelerating

 

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

 

35. The renewable energy source was 10% :/ I put 30%

 

36. The units of capacitance was the one with s^4 (A I think).

 

I can't remember the remaining 4 haha, what were they?

Look Ossih , realy I appreciate that you are grated by skills I don't have and I was proud to ask you, I wish that we all get 7s and the grades we want, but for the electric field strength it is b, closer to 20, since thé ratio of the distances is like 1/4, ratio of charges squared, since e f strength is related to square of distance, like when you have an athlete and some one who does not have good fitness, if you want both to get tired the same way, the athlete has to run more, right? ,

For the mass spectrometer it was one of the straight forward question, same q, double m half v, the doubling of mass will cancel the halving in v, cos they are both in the numerator, but changing q would make a further change, right ?

For the assumptions I don't remember at all that they mentioned temperature which makes me doubt that you may be right, but remember the rubric invites us to chose the best answer and you could some assumptions that won't significantly affect the physics, this is mentioned in the subject report, you know for example, when in p1 they ask you wht is b energy, we would all chose energy.... To separate the nucleus from nucleons, but the answer is to form a nucleus from its nucleons, Do you remember the question about which process will increase the entropy of the local surroundings? In m14 hpm tz2, the answer was isothermal expansion and it should be compression according to Ib past papers not only my understanding, wht do you think

The remaining 4 questions are the new wavelenth when the voltage is quadrupled, the 4 bits possible combinations which I oppose because it is simply about memorizing that it is 2 to the power of n, and I did not know that it is in our s guide, I chose 8 as I thought that zeros in the beginning cannot exist otherwise no difference between , 3 , 4, 5 bits number because both 001 and 01 gives the same decimal number right, but they are 3 and 2 bits, My opposition also is because as you said Ossih the questions demanded a lot of thinking, and this makes me like what I am doing , but that digital technology topic, what are the physics in it, and the energy topic, they are very easy topics but requires a lot of memorizing,

And the other 2 remaining is the question after that of the e field strength of 0 which asked when the electron goes out of the field what happens to its velocity and acceleration, that it is v is increasing, a is decreasing, do you remember it is related to the question in q9 about why the average speed of the electron does not increase, and the last one is the waves question about the rope, and the reflection and inversion,my he wave pulse, Btw I struggled to remember half of those question on Friday even with the help of some friends, but once you remember one you get the others.

What options do you take Ossih?

 

Pretty sure you can define binding energy either way. Maybe it was one mark for converting mm to m? How did you solve the question, anyway?

No , no marks for mm, maybe for converting from e V to Joules but not for an SI prefix, I tried to use Doppler equations but the result was very weird leading to very small change in frequency, so I left it as v over lambda.

[Sofia.]

Hm, weird. Maybe they were generous with the points. Hopefully our answer is right  

[Hassan76]

Maybe there was one one mark for recognizing that they form a standing wave so must have the same frequency !

Soffia would you like to make a quick revision for the astro option as we both take it and invite others,,?

[Hassan76]

Maybe since the waves were reflected so the wavelenth should be doubled ?

[Hassan76]

But Sofia wait a second, we know that the horizontal component is constant, so if it was zero initial velocity, it would stay zero, but when it is vertically upwards there is horizontal velocity otherwise it won't follow a trajectory, I hope this question will be commented on and discounted.

[Hassan76]

Ossih was there an option for twic the mass and twice the charge and v not changed ?

[Sofia.]

But Sofia wait a second, we know that the horizontal component is constant, so if it was zero initial velocity, it would stay zero, but when it is vertically upwards there is horizontal velocity otherwise it won't follow a trajectory, I hope this question will be commented on and discounted.

 

Well yes, exactly. On the graph, the horizontal velocity was not zero, so couldn't have been vertically upwards. It must have been fired with an angle above the horizontal. 

Ossih was there an option for twic the mass and twice the charge and v not changed ?

Yeah I picked that one, but I thought both that one and the velocity changed seemed to work! 

[Ossih]

 

Thanks Vioh! I think you may be right for the temperature one. But this site http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phases_of_Matter/Gases/Kinetic_Theory_of_Gases/Kinetic_Theory_of_Gases states both as assumptions of the Kinetic theory so I really don't know. My book only states elastic though, so maybe that's what it is. Oh well, we'll find out soon enough ahha

 

Yeah, I can't deny the fact that many sources consider the proportionality relationship as an assumption of the kinetic theory. So perhaps you are also correct. You know what, maybe this is one of the questions where there are 2 correct answers Hopefully that is the case!!!

 

However, for the photocurrent one, I'm sure, because it said that the number of photons per second is the same, (it doesn't say the same intensity of light, that would give a different result) implying that the number of electrons per second is the same (assuming that we're above threshold frequency). Because of that photocurrent must stay the same. 

 

If it were same intensity of light, then I agree, the photocurrent would change

 

Not really! We know that the intensity of light is the same. This is because intensity depends only on the number of photons; and since earlier you said that the same number of photons was used, that's why the intensity must be the same!

 

Now, there're 2 ways that the current can increase in a photoelectric experiment, either by:

• Increasing the intensity of light (i.e. the number of photons) --> This works because with more photons, more electrons would get emitted (as each electron can only absorb one single photon). However, since the question says that the number of photons (i.e. intensity) is kept the same, we need not worry about this case.
• OR by increasing the frequency of light --> This works because increasing the frequency means an increase in the energy of the photon (as E=hf), leading to an increase in the kinetic energy (and hence, the velocity) of the electrons. Here, you must realize that current is the amount of charge passing through a point in space per second. So as the electrons have more kinetic energy and velocity, more electrons would pass through that point in space per second, resulting in a larger current. In other words, even though the total number of electrons emitted is the same (as indicated by the same number of photons), but this has nothing to do with the current, because the current is defined as charge passing through a point per unit time.

 

 

No not at all. Intensity is not a measure of the number of the photons but rather a measure of the total energy of photons. Increasing the intensity changes the photocurrent, precisely! They're keeping the number of photons the same, but firing them with a higher energy. Which means that the electrons have higher kinetic energy, but even if this does increase their speed, this does not mean that the current increases! The current is the charge over time. The total charge is determined by the total number of electrons, NOT on their speeds or energies. The total number of charge is the same.

 

Consider this mathematically. Each photon previously had an energy of say 200J. This was divided between the work function, and the kinetic energy of the electron. Now, each photon has say 400J. The work function is the same, so the kinetic energy has increased. BUT kinetic energy of the electron doesn't have anything to do with the current! Rather, it affects the voltage because eV = 1/2mv^2 for an electron remember from Topic 5? You will increase the potential difference but NOT the actual charge/current. The current is solely the charge divided by time, and the charge hasn't changed. I think you have this picture in your head that they're moving faster, and maybe they are, but the effect of that, even though its contrary to intuition, is to increase the potential difference. Because the electrons have greater kinetic energy, they require a greater stopping potential to stop. It does not affect the photocurrent! I am positive haha. 

 

I think you have to remember that intensity is NOT the same as the number of photons It is dependent on the number of photons, but

 

Intensity = Number of photons * energy of photons = Nhf. An increase in the frequency of photons in fact, increases the intensity of the beam (not leading to a corresponding increase in photocurrent however). However because the number of emissions of electrons per unit time is the same, charge per unit time is the same and the current is the same.

[Ossih]

 

 

Guys what about the potential divider question in p1 , and the projectile, and the equipotential, equiptential was for same masses and same charges, projectile was vertically upward since initial vertical v is not 0, as some times when it is launched horizontally initial v in the vertical component is 0 as in May tz1 hp2, potential divider it had a 0 but don't know at the beginning or at the end, electron was accelerating at a decreasing rate and speed was increasing, and this was related to the question about the average speed in 9 in paper 2. And it was in m13 hp2 tz1, equations of motion, constant net force and fixed mass so that a is constant, graph always accelerating since the slope the graph is never parallel to the x axis but v is 0 at an instant so it is not always moving, first question is 3 as 10^_-27 and 10^ -30 , and it is not unfamiliar, the girl's gain in me is 600 areas of the three triangles, entropy of the universe increasing for the melting ice, for isothermal work is greater than adiabatic and delta u is 0, for the gravitational potential it is - 2GM / R +r since it is a scalar, if the question was asking what is the gravitational field strength which is a vector it would be 0, emissivity different temperature same, greenhouses gases was last one, resolution was violet, circle was frequency constantly varying, wave velocity to the right was A, when the slope is increasing, u tube I think it is d as initial displacement doesn't mean no 0 initial velocity and the liquid's motion is damped but I chose a as it is oscillating so v is positive and negative, for the momentum the last one was not valid, for the electric field strength it was b , closest to - 20 , for the maximum power in one of the resistors it is VI not 2VI, for the artificial transmutation it was easy, c I think as I do not remember the choices, for the kinetic model assumption it is elasticity of collisions, for the equilibrium temperature between water and paraffin it is 60 degrees, for the centripetal acceleration it was very easy, for the higher frequency couloir a higher photo current and a larger (more negative) stopping potential, for the evidence of nuclear energy levels it is the discrete nature of alpha and gamma, for the power of the wave it is p over 2, for the wavelenth of 4 V it was half the de broglie wavelenth, for the mass spectrometer it is half v and twice the mass, for the resistance the ratio was 8:1, as d/2 will multiply the area by 0.25, for the alpha particles deflection it is maximum for n at theta equal 0 and minimum when theta is near 170, for the frequency and the halved le th it is still 500 Hz as th the closed end will give wavelenth = 4 * L/2 , which is still 2 L, for the coil I chose the first one, positive sine for the current, for the direction of the force I chose A,

Concerning the question that asked what is not possible is momentum: momentum is given by h/ lambda, electron box model states that the wavelengths can be 2L/n where n is an integer, so 2l, l, 2/3, L/2, 2l/5' 2L/6 etc......,

For the sl, the question about gravitational field strength it is 20,

What do you guys think, plz share with me

 

 

1.The potential divider was actually a potentiometer this year which I've never seen them ask before. It's the graph going from 0 to 3 as a straight line.

 

2.For the projectile, it was fired above the horizontal.

 

3.For the equipotentials, yeah, same mass and same charges. 

 

4. The electron accelerating thing, damn you're right haha I did that one wrong.

 

5. Yeah, constant net force and fixed mass.

 

6. Yeah the first question, the ratio of the orders of magnitude was 3.

 

7. The girl's gain in energy is 600J yup

 

8. Entropy of the universe increases, yea

 

9. For isothermal, ∆U = 0 and work done is greater than adiabatic yup

 

10. Yup, its -2GM/(R+r) cause you add potentials as scalars.

 

11. I don't remember the emissivity question hm.

 

12. Greenhouse gases, they transmit radiation from the sun but absorb radiation from the Earth.

 

13. Resolution was to replace with a violet light yea

 

14. The moving sound source in a circle would be heard with constantly varying frequency, yeah

 

15. Yeah the wave velocity to the right was A.

 

16. U tube was D, the damped one. 

 

17. Hm, for the electric field strength one, I chose A, the one furthest from both. 

 

18. Yeah its VI

 

19. Yes, artificial transmutations was C.

 

20. For kinetic model, I didn't put elasticity of the collisions because they didn't say the it was perfectly elastic. Instead, I chose that the temperature is proportional to the average kinetic energy of the molecules. According to Wikipedia (not that it's the best source haha), one of the assumptions of the kinetic model is that the absolute temperature is a measure of the average kinetic energy of the particles.

 

21. For the water and paraffin, it was 60º yup

 

22. For the photocurrent one, I disagree. The question said that they fired a higher frequency BUT the same number of photons, which means that the number of electrons are ejected and hence the photocurrent is the same. All it is that the stopping potential is now more negative.

 

23. For evidence of nuclear energy levels, its alpha and gamma yup

 

I can't remember the power of the wave and de Broglie wavelength questions.

 

24. For the mass spectrometer, I chose twice the mass, twice the charge and same v. My reasoning is this: For the mass spectrometer, mv^2/r = Bqv right, which gives me r = (mv)/(Bq). B is a constant. Now, both twice the mass and twice the charge, and twice the mass but half the velocity give me the same value of r. So I was confused. But I reasoned that in a mass spectrometer, it wouldn't even enter the deflection area if it had a velocity of v/2! That's the job of the velocity selector, everything comes out with velocity v. So I chose twice the mass and twice the charge.

 

25. For resistance the ratio was 8:1 yup

 

26. For the alpha particles deflection, you're right, its a peak at 0 and falls down.

 

27. Yeah, for the frequency where the length is halved but closed at one end, it remains the same.

 

28. For the coil, I chose positive cos but I'm not even bothered explaining why haha, but I think you're right.

 

29. For the direction of force, I got C! The current was into the page, B was from left to right, and my left hand rule gives me the force as downwards

 

30. For the electron in a box, momentum cant be h/4L because no n in nh/2L will give you h/4L

 

Btw holy crap haha you have a great memory.

 

Others that I remember

 

31. Albedo was water < desert < snow

 

32. The last question (about the potential difference on a pixel) was nNe/C

 

33. The 2/3rd question (the one with the graph), she is constantly accelerating

 

34. The direction of v and a for the electron orbiting a proton, v was tangential and a was to the centre

 

35. The renewable energy source was 10% :/ I put 30%

 

36. The units of capacitance was the one with s^4 (A I think).

 

I can't remember the remaining 4 haha, what were they?

Look Ossih , realy I appreciate that you are grated by skills I don't have and I was proud to ask you, I wish that we all get 7s and the grades we want, but for the electric field strength it is b, closer to 20, since thé ratio of the distances is like 1/4, ratio of charges squared, since e f strength is related to square of distance, like when you have an athlete and some one who does not have good fitness, if you want both to get tired the same way, the athlete has to run more, right? ,

For the mass spectrometer it was one of the straight forward question, same q, double m half v, the doubling of mass will cancel the halving in v, cos they are both in the numerator, but changing q would make a further change, right ?

For the assumptions I don't remember at all that they mentioned temperature which makes me doubt that you may be right, but remember the rubric invites us to chose the best answer and you could some assumptions that won't significantly affect the physics, this is mentioned in the subject report, you know for example, when in p1 they ask you wht is b energy, we would all chose energy.... To separate the nucleus from nucleons, but the answer is to form a nucleus from its nucleons, Do you remember the question about which process will increase the entropy of the local surroundings? In m14 hpm tz2, the answer was isothermal expansion and it should be compression according to Ib past papers not only my understanding, wht do you think

The remaining 4 questions are the new wavelenth when the voltage is quadrupled, the 4 bits possible combinations which I oppose because it is simply about memorizing that it is 2 to the power of n, and I did not know that it is in our s guide, I chose 8 as I thought that zeros in the beginning cannot exist otherwise no difference between , 3 , 4, 5 bits number because both 001 and 01 gives the same decimal number right, but they are 3 and 2 bits, My opposition also is because as you said Ossih the questions demanded a lot of thinking, and this makes me like what I am doing , but that digital technology topic, what are the physics in it, and the energy topic, they are very easy topics but requires a lot of memorizing,

And the other 2 remaining is the question after that of the e field strength of 0 which asked when the electron goes out of the field what happens to its velocity and acceleration, that it is v is increasing, a is decreasing, do you remember it is related to the question in q9 about why the average speed of the electron does not increase, and the last one is the waves question about the rope, and the reflection and inversion,my he wave pulse, Btw I struggled to remember half of those question on Friday even with the help of some friends, but once you remember one you get the others.

What options do you take Ossih?

 

 

There was an option for twice the mass and twice the charge :$ If you did um, chemistry, you'd know from topic 2 that deflection depends kinda solely on the charge-to-mass ratio, because the velocity when coming out of the velocity selector cannot change.

 

I do astrophysics and relativity, you?

[Sofia.]

Exactly, that's why I picked that one instead of the change in velocity. 

[Hassan76]

Yes I do chemistry SL Ossih and Maths HL stat and prob, but 1- I know double mass and charge is correct but I didn't take care of it, 2- take care in chemistry we don't have the bain bridge mass spectrometer, I think it's Aston's, and in chem deflection is proportional to q and 1/m, in physics it is the opposite. I do astro and medical

Sorry guys I was wrong, I confused the radius with deflection, thought that the greater it is the greater the deflection

Edited May 12, 2015 by Hassan76