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Can light be bent around an object, so that it would show the light on the other side with out absorbing it? For example, --/o\-- The o is the object, the dashes are the light, and the slashes are also light, just being put around the object. I would like to know if this is possible, and if yes, what is it called?
- Jon Stoffel (age 15)
The Kings Academy, Marion, IN, U.S.A.
Yes, it's possible. It's called diffraction. it happens because light
is a type of wave. You've seen water waves hit logs, rocks, piers, etc.
When the do, you can see the wave spread out again behind the object.
If the wavelength (the space from crest to crest) is small compared to
the object, there can be a pretty sharp wave-free shadow behind the
object. Otherwise, the diffraction spreads out the wave so that little
or no shadow is found. The wavelength of light is small compared to
many of the things we look at, so usually we don't have to think about
the diffraction. High-magnification microscopes are used, of course, to
look at very little things. Then diffraction becomes very important-
it's the main limit on how small a thing you can see with a microscope.
(published on 10/22/2007)
Follow-Up #1: diffraction and interference.
Could you please explain why it bends? I read somewhere that it is due to the interference of secondary waves. Does it mean that diffraction is also a kind of interference?
In a way, it's the reverse. Starting from any little region, the wave would propagate out in all directions. Interference between parts of the wave starting in different regions makes it propagate in a more limited set of directions. The interference isn't perfect, because the objects aren't infinite numbers of wavelengths in size. So the wave still propagates in a somewhat fuzzy set of directions. That means it spreads out rather than following simple ray paths.
(published on 09/30/10)
Follow-up on this answer.