(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 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 determines the intensity of light in the photon picture of light.
Reflection and refraction arise through the interaction of incident light with the atomic constituents of matter. Atoms act as oscillators that take up the frequency of the external agency (light), causing forced oscillations. Since the frequency of light emitted by a charged oscillator equals its frequency of oscillation, the frequency of scattered light equals the frequency of incident light.
No, the reduction in speed does not imply a reduction in the energy carried by the light wave. The energy carried by a wave depends on the amplitude of the wave, not on the speed of wave propagation. Therefore, the energy remains unchanged despite the decrease in speed.
In the photon picture of light, for a given frequency, the intensity of light is determined by the number of photons crossing a unit area per unit time.
Explanation
The answers are derived directly from the solution provided in Example 10.1 of the textbook context. Part (a) explains frequency conservation via atomic oscillations. Part (b) clarifies that energy depends on amplitude, not speed. Part (c) defines intensity in the photon model based on photon flux.