Question

In a photo diode the conductivity increases when the material is exposed to light. It is found that the conductivity changes only if the wavelength of incident light is less than 500 nm. What is the band gap? Use `h=6.6xx10^(-34)Js, c=3xx10^(8) ms^(-1)`.

Answer 1

`E_(g)=(hc)/lambda=((6.6xx10^(-34))xx(3xx10^(8)))/(500xx10^(-9)xx1.6xx10^(-19))eV`
`2*475 eV=2*48 eV`