Question

Consider light energy that is momentarily absorbed in glass and then re-emitted. Compared to the absorbed light, the frequency of the re-emitted light is
A) considerably less.
B) slightly less.
C) the same.
D) slightly more.
E) considerably more.

Answer 1

Answer:

Compared to the absorbed light, the frequency of the re-emitted light is the same.

Explanation:

The reason to why the light energy that is momentarily absorbed in glass and then re-emitted, compared to the absorbed light, the frequency of the re-emitted light is the same is because the wavelength of the absorbed light and the re-emitted light is the same. The energy carried by an electromagnetic wave is proportional to the frequency of the wave. The wavelength and frequency of the wave are connected via the speed of light:

c = fλ

where

• c is the speed of light
• f is the frequency of light
• λ is the wavelength of the light

Though light does not have mass, it does have energy and it's energy is conserved. Therefore, in the conservation of energy, the energy of the absorbed light must be equal to the re-emitted light. This is why the frequency of the re-emitted light is the same as the frequency of the absorbed light.