“…The value of n is an index which can be assumed to have values of 2, 3, 1/2 and 3/2, depending on the nature of the transition responsible for the absorption (for indirect allowed transition, n = 2, and for indirect forbidden transition, n = 3; for direct allowed transition, n = 1/2 and for direct forbidden transition, n = 3/2) [18][19][20]. The type of optical transition can be determined using Eq.…”