1. The problem statement, all variables and given/known data 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. 2. Relevant equations Don't know. 3. The attempt at a solution Did not try yet as i don't know how to.