What causes light to bend when passing the edges of objects?

[bwana]

Please forgive my density but consider a slit:
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Now magnify the slit until you see the edges
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The edges of the slit actually have thickness. (I am not talking about the gap, I am referring to the thickness of the material in which the slit is cut)

Does diffraction change as the material gets thinner and thinner? In other words, is the diffraction greater if the material is thinner than the wavelength ?

Experimentally, I think it would be easier to increase the wavelength and keep the material the same, but you get the idea.

 

[sophiecentaur]

Of course the edges must have an effect. All real objects have depth and they produce their peculiar diffraction patterns. If you take it to an extreme, you could have two 'pipes' with light emerging and they would also have a distinct pattern - but whether you could detect the difference would be another matter.

Remember that a hologram is merely the diffraction pattern of a three dimensional object.