(a) The energy gap between the valence band and the conduction band in silicon is 1.14 eV at room temperature. What is the wavelength of a photon that will excite an electron from the top of the valence band to the bottom of the conduction band? Do the same calculation for

(b) Germanium, for which the energy gap is 0.72 eV, and 

(c) For diamond, for which the energy gap is 7.0 eV.