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Single Slit Defraction
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Light, traveling through a small slit, creates an interference pattern which shows up as a pattern of light and dark lines, (middle line being largest and brightest). I'm wondering why this happens? What's causing the interference to have the light and dark lines show up? 
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Re: Single Slit Defraction
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on 2010-07-04 11:39:40 (edited 2010-07-04 11:41:15)
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Correct me if i'm wrong but isn't this something to do with the phases of the light waves? If you think of the phasors of the light waves, the central line is the brightest because the light passes through the slit in a straight line from the small slit to the screen so all of their phasors point in the same direction; all of the light waves are in phase. (they add up forming a large resultant phasor). For the dark fringes, the phasors of the light waves adds up to form a circle (the resultant phasor is zero). |
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Re: Single Slit Defraction
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on 2010-07-04 14:32:18 |
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It also has to do with wave-particle duality. The experiment is done with a screen that absorbs protons, but the pattern they form can only be from the light waves either boosting each other or cancelling each other out. I'd also recommend looking up the double-slit experiment. That's when it gets really cool.  |
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Re: Single Slit Defraction
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Thanks! My textbook didnt really explain it at all so this is a lot of help. I do know about the double-slit diffraction experiment (by Young if my memory is correct). I found it easier to understand the light coming through each slit acts as a point source for the waves as opposed to the multiple point sources that form with the single slit.
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Re: Single Slit Defraction
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on 2011-03-07 23:25:49 |
| According to Huygens principle ,the light waves reaching the slit ,spread in all directions (forward only). so, on the screen at some places the light waves are in phase , while at other places they are out of phase due to path difference. hence we get alternate dark and bright fringes , which can be explained by using geometry. For a better explanation refer NCERT physics book for class 12 . |