PHYSICS HL MAY 2010 DISCUSSION

[hanniexx]

I just remembered something. I noticed a kind of contradiction in a question in P1. (I'm TZ2 btw)

umm I don't quite remember the question, but the answer choices talk about the greatest/least minimum/maximum wavelength/frequency. The answer is like a combination of these words. However one of the answers mentions "greatest minimum wavelength". What in the world is that supposed to mean?

Did anyone else notice this or am I alone?

I just took it to be the greatest maximum wavelength and I answered that choice by elimination, since I thought all the others were wrong.

Any thoughts on this? or am I starting to imagine things? Or am I just an English grammar failure?

Was this one a part A and part B question, can you remember? I'm not sure if I noticed it if it was a part A, part B I may not have done it

[tdubthebassist]

I just remembered something. I noticed a kind of contradiction in a question in P1. (I'm TZ2 btw)

umm I don't quite remember the question, but the answer choices talk about the greatest/least minimum/maximum wavelength/frequency. The answer is like a combination of these words. However one of the answers mentions "greatest minimum wavelength". What in the world is that supposed to mean?

Did anyone else notice this or am I alone?

I just took it to be the greatest maximum wavelength and I answered that choice by elimination, since I thought all the others were wrong.

Any thoughts on this? or am I starting to imagine things? Or am I just an English grammar failure?

speed of light is constant. Hence greater wavelength implies smaller wavelength...

So if you are below the wavelength, higher frequency it means, hence you will go over the threshold, and therefore, you got the right answer. So what they meant by that was 'below the threshold wavelength'.

Similar question on atomic energy level question. it said largest wavelength and smallest wavelength, each of which means lower E and higher E. So it has to be 4-3 and 4-1. (4 was the highest one I think?)

... and btw, paper 2 section A first question. it was theory 1. that was the one within the boundary of random error.

Edited May 11, 2010 by tdubthebassist

[IBer_101]

Was this one a part A and part B question, can you remember? I'm not sure if I noticed it if it was a part A, part B I may not have done it

It's a multiple choice Paper 1 question, just one part. I think it's about photoelectric emissions in metals.

[hanniexx]

speed of light is constant. Hence greater wavelength implies smaller wavelength...

So if you are below the wavelength, higher frequency it means, hence you will go over the threshold, and therefore, you got the right answer. So what they meant by that was 'below the threshold wavelength'.

Similar question on atomic energy level question. it said largest wavelength and smallest wavelength, each of which means lower E and higher E. So it has to be 4-3 and 4-1. (4 was the highest one I think?)

... and btw, paper 2 section A first question. it was theory 1. that was the one within the boundary of random error.

Yay! ^^

I do remember that question, it was a trick question I think. They probably sort of expected you to put the frequency one, knowing that there is a threshold frequency. But you had to work it out, and it was the wavelength answer.

[IBer_101]

speed of light is constant. Hence greater wavelength implies smaller wavelength...

So if you are below the wavelength, higher frequency it means, hence you will go over the threshold, and therefore, you got the right answer.

Similar question on atomic energy level question. it said largest wavelength and smallest wavelength, each of which means lower E and higher E. So it has to be 4-3 and 4-1. (4 was the highest one I think?)

... and btw, paper 2 section A first question. it was theory 1. that was the one within the boundary of random error.

You mean to say that greater frequency implies smaller wavelength? Even though, the question should just say the greatest maximum wavelength, not the greatest minimum wavelength, cos that makes no sense/is confusing to me.

I answered 4-1 least wavelength and 4-3 largest wavelength for that question.

I thought it was theory 1 also =) since the slope of the second graph is 1/3. you do some algebra and it turns out that theory 1 fits that slope

[tdubthebassist]

one question.

that Schrödinger model question... a bit of argument can happen.

B and D were basically related to each other. even though the model is based on wave-particle duality, it can also be described by wave functions...

I choose B because it was more likely (it was more fundamental!) but D would have also made sense...

[metroid02]

Paper 1 and paper 2 were pretty good. I always have a pretty good feeling about them and usually get a 7 so lets hope this was the case again. I picked B1 and B2 and answered everything. I was kinda wavering to do the question about momentum and force, but the second part of that was digital tech I believe so that question was definitely out. Paper 3 was not as great. Forgot how to do one of the questions on relativity. Also misread a question that said DONT use this example. Of course I used that example. Explanations on relativity are quite tough so I don't expect too much of them. Still hoping for a seven though since I felt pretty good about astrophysics.

I realize this is my first post and all but I just want to advise you that until tomorrow we are NOT allowed to talk about the Paper 3. =)

As for the first paper, I dont think I did very well on it. The questions were pretty tricky and only on a few am I sure I got them right. As for paper 2 (TZ1), Section A was pretty easy, the first one with the lgR = a + b/T was pretty tough though (IMO). I chose parts B2 and B4. I was about to choose B3 instead of B4. Reason being, the topics from B3 I kinda knew (meaning I could get partial credit at least on each question) but in the case of B4 I was 100% confident that I could get Part 1 (the circuit and resistor questions) right, but on the second part I knew that I could maybe milk a point or two there. So i decided that overal B4 was gona give me more points. I felt pretty good about that one and finished with 15 minutes remaining.

[hanniexx]

one question.

that Schrödinger model question... a bit of argument can happen.

B and D were basically related to each other. even though the model is based on wave-particle duality, it can also be described by wave functions...

I choose B because it was more likely (it was more fundamental!) but D would have also made sense...

I remember thinking that. What was B again? D was the wave-function, right?

Coming back to think of it...I remember thinking it said the electron was a wave-function. But that's a little iffy, isn't it? Because the wave-function is just the probability of finding the electron in a particular place, not the actual electron itself. So I think that's why D is wrong. I think.

Edited May 11, 2010 by hanniexx

[tdubthebassist]

one question.

that Schrödinger model question... a bit of argument can happen.

B and D were basically related to each other. even though the model is based on wave-particle duality, it can also be described by wave functions...

I choose B because it was more likely (it was more fundamental!) but D would have also made sense...

I remember thinking that. What was B again? D was the wave-function, right?

Coming back to think of it...I remember thinking it said the electron was a wave-function. But that's a little iffy, isn't it? Because the wave-function is just the probability of finding the electron in a particular place, not the actual electron itself. So I think that's why D is wrong. I think.

BUT wave function arises when electrons are waves. So technically it makes sense both way. wave-particle duality of an electron is the basis of that model...

[IBer_101]

one question.

that Schrödinger model question... a bit of argument can happen.

B and D were basically related to each other. even though the model is based on wave-particle duality, it can also be described by wave functions...

I choose B because it was more likely (it was more fundamental!) but D would have also made sense...

I remember thinking that. What was B again? D was the wave-function, right?

Coming back to think of it...I remember thinking it said the electron was a wave-function. But that's a little iffy, isn't it? Because the wave-function is just the probability of finding the electron in a particular place, not the actual electron itself. So I think that's why D is wrong. I think.

BUT wave function arises when electrons are waves. So technically it makes sense both way. wave-particle duality of an electron is the basis of that model...

I think D was that the electron can be expressed in terms of the wave function, right? I chose this answer since this is completely right, without any doubt.

However, when B says electrons are waves, this might be cast doubt upon since electrons do not ALWAYS act as waves; they have wave-particle duality. So, since B may be cast doubt upon this way, I thought D was the more suitable answer.

[hanniexx]

one question.

that Schrödinger model question... a bit of argument can happen.

B and D were basically related to each other. even though the model is based on wave-particle duality, it can also be described by wave functions...

I choose B because it was more likely (it was more fundamental!) but D would have also made sense...

I remember thinking that. What was B again? D was the wave-function, right?

Coming back to think of it...I remember thinking it said the electron was a wave-function. But that's a little iffy, isn't it? Because the wave-function is just the probability of finding the electron in a particular place, not the actual electron itself. So I think that's why D is wrong. I think.

BUT wave function arises when electrons are waves. So technically it makes sense both way. wave-particle duality of an electron is the basis of that model...

Yeah, no no I get you. But I think D said 'electrons can be described as wave-functions.' I take that to mean that the wave functions are the electrons, which isn't true, as you say. The wave function only arises when the electrons are waves, but the electrons themselves are not wave functions. Wave functions are a product of the electrons being waves. The wave function is only a probability.

I think we're agreeing on the same thing, just saying it differently haha

[tdubthebassist]

one question.

that Schrödinger model question... a bit of argument can happen.

B and D were basically related to each other. even though the model is based on wave-particle duality, it can also be described by wave functions...

I choose B because it was more likely (it was more fundamental!) but D would have also made sense...

I remember thinking that. What was B again? D was the wave-function, right?

Coming back to think of it...I remember thinking it said the electron was a wave-function. But that's a little iffy, isn't it? Because the wave-function is just the probability of finding the electron in a particular place, not the actual electron itself. So I think that's why D is wrong. I think.

BUT wave function arises when electrons are waves. So technically it makes sense both way. wave-particle duality of an electron is the basis of that model...

I think D was that the electron can be expressed in terms of the wave function, right? I chose this answer since this is completely right, without any doubt.

However, when B says electrons are waves, this might be cast doubt upon since electrons do not ALWAYS act as waves; they have wave-particle duality. So, since B may be cast doubt upon this way, I thought D was the more suitable answer.

well, they behave like waves AND particles AT THE SAME TIME. BUT the model was assumed on the basis of 'election in a box' model which completely see electron as a wave. and wave function of election implies that electrons are behaving as waves.

[hanniexx]

ABOUT THIS SCHRODINGER MODEL QUESTION:

The Physics textbook says:

1. The description of particles in quantum is in terms of a wave function. This function has no physical meaning but the square of the wave function does.

2+3. The function has different values, and develops with time and interacts with other wave functions.

The wave functions provides a way or working out the probability of finding an electron at that particular radius.

Therefore, it can't be D. Nowhere does it say that the electron can be described as a wave function. This is only the probabilty.

However, on another page, it says:

Electrons can be described as waves

which then leads into the electron in a box model.

I can't remember exactly what B was - what was it? - but it can't be D.

(Or do I just not understand and should shtum x.x)

Edited May 11, 2010 by hanniexx

[IBer_101]

ABOUT THIS SCHRODINGER MODEL QUESTION:

The Physics textbook says:

1. The description of particles in quantum is in terms of a wave function. This function has no physical meaning but the square of the wave function does.

2+3. The function has different values, and develops with time and interacts with other wave functions.

The wave functions provides a way or working out the probability of finding an electron at that particular radius.

Therefore, it can't be D. Nowhere does it say that the electron can be described as a wave function. This is only the probabilty.

However, on another page, it says:

Electrons can be described as waves

which then leads into the electron in a box model.

But you can't say that electrons are waves, and stop there. This is not a full description of the electron. But when you say that they can be expressed in terms of the wave function, this is correct, and it relates to the electron in a box model. It's true that the function in itself has no meaning, but the "description of particles in quantum mechanics is in terms of a wave function". So to say that the electron can be expressed in terms of a wave function is fully correct.

I just find this answer much less likely to be wrong than the other answer since it states the facts correctly without leaving any chance for doubts or "if"s.

[IBer_101]

Choice B said that the electron is a wave I believe, something of that sort.

[tdubthebassist]

ABOUT THIS SCHRODINGER MODEL QUESTION:

The Physics textbook says:

1. The description of particles in quantum is in terms of a wave function. This function has no physical meaning but the square of the wave function does.

2+3. The function has different values, and develops with time and interacts with other wave functions.

The wave functions provides a way or working out the probability of finding an electron at that particular radius.

Therefore, it can't be D. Nowhere does it say that the electron can be described as a wave function. This is only the probabilty.

However, on another page, it says:

Electrons can be described as waves

which then leads into the electron in a box model.

But you can't say that electrons are waves, and stop there. This is not a full description of the electron. But when you say that they can be expressed in terms of the wave function, this is correct, and it relates to the electron in a box model. It's true that the function in itself has no meaning, but the "description of particles in quantum mechanics is in terms of a wave function". So to say that the electron can be expressed in terms of a wave function is fully correct.

I just find this answer much less likely to be wrong than the other answer since it states the facts correctly without leaving any chance for doubts or "if"s.

well, that is why the question said 'it is assumed that...'. 'the model' saw the electron as wave. Not that the electron itself is a wave and only wave. But the 'assumption' of the model is that electrons are waves.

even though, I must admit that one supports the other. if it behaves as a wave, then wave function to describe it must exist. I think the answer would come out 'B AND D'. if not, well no luck for one side of us.

[hanniexx]

ABOUT THIS SCHRODINGER MODEL QUESTION:

The Physics textbook says:

1. The description of particles in quantum is in terms of a wave function. This function has no physical meaning but the square of the wave function does.

2+3. The function has different values, and develops with time and interacts with other wave functions.

The wave functions provides a way or working out the probability of finding an electron at that particular radius.

Therefore, it can't be D. Nowhere does it say that the electron can be described as a wave function. This is only the probabilty.

However, on another page, it says:

Electrons can be described as waves

which then leads into the electron in a box model.

But you can't say that electrons are waves, and stop there. This is not a full description of the electron. But when you say that they can be expressed in terms of the wave function, this is correct, and it relates to the electron in a box model. It's true that the function in itself has no meaning, but the "description of particles in quantum mechanics is in terms of a wave function". So to say that the electron can be expressed in terms of a wave function is fully correct.

I just find this answer much less likely to be wrong than the other answer since it states the facts correctly without leaving any chance for doubts or "if"s.

But there is no way that D can be right because electrons can not be described as a wave function. That's saying that an electron is a probability. No it's not.

What the book goes on to say is that describing it as a wave means that discrete energy levels exists.

Furthermore, the book says that de Broglie hypothesies that anything with matter has a wave.

The book has physically said B is correct, and has not said anything about D.

And this whole topic is about 'ifs' and doubts - no-one knows for sure about wave-duality or wave-functions, it's all hypothesis! But according to those hypothesis, electrons can be described as a wave, but can't be described as a wave function because that function is just a probability, and an electron is not a probability.

[tdubthebassist]

ok. here is the answer. it is B

http://www.colorado.edu/physics/2000/quantumzone/schroedinger.html

second thing he said.

BUT I think the answer must be B and D...

Edited May 11, 2010 by tdubthebassist

[IBer_101]

I do realize that but D doesn't say that the electron is a wave function, it only says that it can be expressed in terms of the wave function. This is correct according to the book. Anyways, I think it's a confusing question. But, the bright side is that, in a worst case scenario, you only lose one mark out of 60 so no worries =)

[hanniexx]

I do realize that but D doesn't say that the electron is a wave function, it only says that it can be expressed in terms of the wave function. This is correct according to the book. Anyways, I think it's a confusing question. But, the bright side is that, in a worst case scenario, you only lose one mark out of 60 so no worries =)

Haha true that.

I love how Physics can be so interesting in this way and can cause such debates. So fun