Band Gaps

The energy gaps between the valence and conduction bands are called band gaps. For silicon, the band gap is 1.1eV; for fused silica glass, it is 9.3eV.

Part C

Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. This works through a process known as multiphoton absorption. In this process, several photons are absorbed at the same time. If very intense light whose photons carry 2eV of energy is shined onto a material with a band gap of 4eV, that light can be absorbed through two-photon absorption, because two photons have the right amount of energy to bridge the band gap. What is the minimum number of photons of 800-nm light that are needed to equal or exceed the band gap of fused silica glass?

Express your answer as an integer.