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Does the single diffraction work for sound wave

  1. Jan 4, 2013 #1
    PIC (A)
    http://imageshack.us/a/img37/941/img20130104192537.th.jpg [Broken]

    PIC (B)
    http://imageshack.us/a/img23/5496/img20130104192554.th.jpg [Broken]

    I hope you can ans it in a simple way as I am just a secondary 6 student :) thx!

    For pic a,
    1. I dun understand why interference occurs when there is 1 slit only. My teacher told me to divide the slit into 2 part. But why ?
    2. Does the single slit diffraction happen when the slit is in circular shape ? Will it work when I use the normal one ? ("young single slit")
    3. Can the single diffraction be demonstrated in water bath ? Just like the experiment of young double slit in water.
    4. Does the single diffraction work for sound wave ?

    For pic b
    1. Why diffraction happen in lens?
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jan 4, 2013 #2


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    Interference happens as soon as there is more than one "way" light can take. In a single slit, you get interference between light passing at the upper edge, the lower edge and everything in between.

    You get interference with every type of slit, but the diffraction pattern depends on the slit geometry.

    You can demonstrate single-slit interference with water waves, but the result does not look so nice. The same is true for sound.
  4. Jan 4, 2013 #3


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    Your teacher may have missed out a step when he told you to divide the slit into two. The fact is that any aperture / hole / slot of finite width allows light to take many paths through it. To find the resulting diffraction pattern it happens to be convenient to divide the slit into two halves and to work out the effect of pairs of infinitely small sources adding together. The problem then reduces to the simple two slit case with the slits very close together and, hence, the spacing between the nulls will be wide.

    There are many times when people choose apparently arbitrary ways of getting solutions to problems (like when you solve simultaneous equations and multiply them and add them so as to eliminate one of the variables - because it works). Why do you take the turnings that you do on your journey home? Because you've done it before and you know the best way. Same thing with all those bits of book work in Science. As you progress with your Science, you will learn all those dodges and they will cease to puzzle you.

    Why do you get diffraction through a lens? Diffraction is the result of limiting the number of paths that the light can take (yes, even the very indirect paths count).The only time there is NO diffraction is when there is a totally unobstructed path from source to image and all lenses have a finite width (aperture). So there will always be some degree of diffraction - less for a wide lens and more for a small lens.

    PS Please avoid text speak abbreviations. It is a matter of courtesy, particularly for the more ancient (and potentially helpful) forum members. There is no character limit for these posts and you wouldn't want to appear 'ignorant', would you?
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