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I was wondering the other day that which phenomenon of light causes that colour display on our Compact Discs. Is it interference or diffraction. Please give the reason also.
It is a combination of the two:Diffraction is the tendency of the edges of a wavefront to radiate circularly so light can go around a corner[diagram=281_0]In a cd the millions of pits will have millions of edges so the light will diffract from all of them.Interference is how two or more light waves interact with one another. If they are moving in time they will add if moving out of time then subtract. So the diffracted light interferes to produce bright and dark patches.Different colours have different wavelengths so their bright and dark patches occur in different places so you see different colours in different places.
I mean there are no slits on a cd. Light cannot pass through it, so howcome it gets bended. I would really appreciate if u could eloborate it to make it clear to me.. Thanx