a. 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.
b. When light travels from a rarer to a denser medium, the speed decreases. Does the reduction in speed imply a reduction in energy carried by the light wave?
c. In the wave picture of light, intensity of light is determined by the square of the amplitude of the wave. What determine the intensity of light in the photon picture of light?

Explanation

a. Reflection and refraction arise through interacion of incident light with the atomic conistituents of matter. Atoms may be viewed as oscillators, which take up the frequency of the external agency (light) causing forced osicllations.The frequency of light emitted by a charged oscillator equals its frequency of oscillation. Thus, the frequency of scattered light equals the frequency of incident light.
b.No. Energy carried by a wave depends on the amplitude of the wave, not on the speed of wave propagation.
c.For a given frequency, intensity of light in the photon is determined by the number of photons crossing a unit are a per unit time.