With the of an energy -momentum (e-k) diagram describe the basic process used to obtain optical gain in semiconductors? explain the difference between direct and indirect band-gap semiconductors. (4) 1. 58 b) with the aid of a suitable diagram, discuss the main design features of a double heterostructure semiconductor laser and explain the role of these features in the optimization of the threshold current. (4)

Diamond will scratch quartz. true or false

Calculate the ratio of h+ ions to oh– ions at a ph = 6. find the concentration of h+ ions to oh– ions listed in table b of your student guide. then divide the h+ concentration by the oh– concentration. record this calculated ratio in table a of your student guide. compare your approximated and calculated ratios of h+ ions to oh– ions at a ph = 6. are they the same? why or why not? record your explanation in table a. what is the concentration of h+ ions at a ph = 6? mol/l what is the concentration of oh– ions at a ph = 6? mol/l what is the ratio of h+ ions to oh– ions at a ph = 6? : 1

Imagine you are standing in the antarctic during the southern hemisphere summer. the sky is clear and blue. there are no clouds in the sky. your shadow is cast on the icy ground. what is the color of the shadow?