Answer to Question #17735 in Quantum Mechanics for Bruce

Question

The gap between valence and conduction bands in diamond is 5.47 eV.
(a) What is the maximum wavelength of a photon that can excite an electron from the top of the valence band into the conduction band? In what region of the electromagnetic spectrum
does this photon lie?
(b) Use your calculations to explain why pure diamond is transparent
and colourless.
(c) Most gem diamonds have a yellow colour. Explain with the help of an
energy diagram how impurities in the diamond can cause this colour.

Explanation will be preferred too. Thank you.