Question

When monochromatic light is incident on a surface separating two media. The reflected and refracted light both have the same frequency as the incident frequency. Explain why ?

Answer 1

Both reflection and refraction occur due to interaction of light with the atoms at the surface of separation. These atoms may be regarded as oscillators. Light incident on such atoms forces them to vibrate with the frequency of light. As the light emitted by these charged oscillators is equal to their own frequency of oscillation, so both the reflected and refracted lights have the same frequency as the frequency of incident light.