Explain the following giving reasons:
(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 the energy carried bythe light wave ?
(c) In the wave picture of light, intensity of light is determined by the square of the amplitude of the wave, what determines the intensity of light in the photon pisture of light ?

Explanation

(a) Refraction and refraction both arise through interaction of incident light with the atomic constituents of matter. Atoms may be considered as oscillators which vibrate with frequency of light. The frequency of light emitted by a charged oscillator equals its frequency of oscillation. therefore, the frequency of both reflected as well as refracted light equals the frequency of incident light.
(b) No. Reduction in speed of light has no connection with energy carried by light wave. energy carried by a wave depends only on its amplitude.
(c) As per photon pixture of light intensity of light is determined by the number of photons of a given frequency crossing per unit area per unit time.