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How can diffraction occur with gap smaller than the wavelength?

  1. Nov 22, 2013 #1
    I was wondering if diffraction of a wave can occur when the gap through which the wave passes is shorter than the wavelength itself. Then I came across this website


    Which says that "In order for this effect to be observed, the size of the object or gap must be comparable to or smaller than the wavelength of the waves."

    I would like to know how can diffraction occur when the wavelength is longer than the gap? Wouldn't it be blocked?

    I don't really understand the mechanism here because every illustration I met just showed some straight and curve lines "as a whole" without drawing out what happens to each single wavelength.
  2. jcsd
  3. Nov 22, 2013 #2


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    The wavelength has nothing to do with the size of light, or anything within the wave picture of light. It isn't an "object".

    I think you need to do some self-analysis of what you know that made you associate the wavelength with a physical size. There's nothing in the physics that would associate those two characteristics together.

    As an analogy, do you see water waves going through openings smaller than its wavelength? Or what about sound going through a very tiny hole?

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