# Gap Band

1. Apr 10, 2008

### vachan

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 800nm- light that are needed to equal or exceed the band gap of fused silica glass?

I tried Energy of photon= hc/$$\lambda$$..... but then after that i dont know what to do. ... i know that energy is the J/ photon......... so i multiply it by the energy in the band.,.... but didnt get it!! anyone knows how to do it?!

2. Apr 10, 2008

### vachan

never mind i got it..