Question

when monochromatic light is incident on a surface separation two media, the reflected and refracted light both have same frequency. Explain why?

Answer 1

THE ANSWER IS:

• In refraction and reflection the incoming electromagnetic wave causes the electron density of the refracting material to oscillate.
• This happens because at any point in space the wave produces an oscillating electric field (and magnetic field, though that isn't relevant here) so any material that has a non-zero polarisability will respond by developing an oscillating dipole. This oscillating dipole then emits EM radiation, as any oscillating dipole will do.
• However the emitted wave will have a phase shift relative to the incoming wave, and this causes the velocity of the EM wave in the solid to be different from the speed in the vacuum.
• Hence the refractive index is different from 1 and we get refraction and reflection. A search of this site will find several questions that go into this process in more detail.
• The point of all this is that the oscillations of the electron density in the material are at the same frequency of the incoming wave because they are driven by it. Therefore the frequency of the reradiated light is also the same frequency as the incoming wave. The process cannot change the frequency of the light.

Answer 2

Answer:

i am agree with the statement but i dont know the reason