Energy Levels in Atoms and Line Spectra problem 17

A photon is a packet of energy of electromagnetic radiation. It is the smallest possible amount (or quantum) of electromagnetic energy. A photon carries energy that is directly proportional to its frequency , the energy is given by the equation:

where is Planck’s constant.

The energy of a photon of light of wavelength is .

Photons of light incident on the semiconductor material give energy to the electrons in its valence band, and since the photon energy is greater than the energy of the forbidden band, the electrons, therefore, become excited and move into the conduction band, leaving holes in the valence band. These electrons and holes are charge carriers, which increase the current in the semiconductor material, leading to a decrease in its resistance.