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)

Abox that has self-contained cable clamps holds two light switches. a two-wire no. 12 cable with ground feeds the box, and a pair of two-wire no. 12 cables (four conductors) with ground wires leaves the box to feed the light fixtures. the second switch is fed by a no. 12 jumper wire from the first switch. which one of the following box combinations would furnish the minimum allowable volume? a. two 3-inch × 2-inch × 21⁄2-inch gangable device boxes b. two 3-inch × 2-inch × 11⁄2-inch gangable device boxes c. two 3-inch × 2-inch × 23⁄4-inch gangable device boxes d. two 3-inch × 2-inch × 21⁄4-inch gangable device boxes