Grassroot Posted August 4, 2011 Report Share Posted August 4, 2011 I am a HL student taking exam in May 2012. I have some problems understanding single and double slit diffraction. I do get the principle and formation of them, (ie. diffraction) but I don't really understand the graph shown in single or double diffraction,especially the graph of maxima and minima. Can any genius in physics give me a brief introduction and explanation of the topic above? Thanks. Reply Link to post Share on other sites More sharing options...
Ezeh Posted August 6, 2011 Report Share Posted August 6, 2011 (edited) So, for single slit diffraction, you get a diffraction pattern which is graphed as maximums and minimums. With a small slit, each side/edge of the slit acts as a point source. The central maximum is simply the middle point when these two waves meet. In this case, they have travelled the same distance, and therefore are completely in phase. As a result, the resultant wave is due to the constructive interference between the two, hence why this is seen as a light shade on the diffraction pattern. The next part is the first minimum. This can be visualised by imagining a point that is slightly above or below the central maximum. Minimums are a result of destructive interference, as hence the first minimum is when one wave has travelled further then the other wave, putting it completely out of phase. This difference is known as the path difference. As you can imagine, the other maximums and minimums that follow are a result of constructive and destructive interference as well. If they are out of phase, then it is constructive, and if it is out of phase, then it is destructive. You will also be required to do calculation regarding the slit width (b), the angle of the first minimum from the normal of the slit (theta), as well as the wavelength. The formula which is in the data booklet is . You will however need to derive this formula, so if you need me to help you with that I can. Heres some pictures i just drew up to help: Double slit is basically the same, however there is no central maximum, there are just shades of light and dark areas. The light intensity graph simply varies from high to zero as you move along the screen (position). If you increase the distance between the two sources, then the fringe pattern will also space out. Edited August 6, 2011 by Ezeh Reply Link to post Share on other sites More sharing options...
IB-Adam Posted August 9, 2011 Report Share Posted August 9, 2011 Sorry if I am not answering your question now, but I think that diffraction by double slits isn't in the syllabus. Reply Link to post Share on other sites More sharing options...
Ezeh Posted August 10, 2011 Report Share Posted August 10, 2011 Sorry if I am not answering your question now, but I think that diffraction by double slits isn't in the syllabus. It isn't, but there's not much to it that's different to single slit. Besides it pays off knowing about it because you will need to answer questions about two source interference and double slit diffraction grating. Reply Link to post Share on other sites More sharing options...
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