b) A laser system has a cavity with reflectivities 0.7 and 0.5, and the internal losses are 2%.
Find total logarithmic losses per round trip. Calculate threshold inversion $N_c$ if length of
active medium is 5 cm and transition cross section $2 \times 10^{-19}$ cm².
c) If the diameter of laser beam is 2 mm and power is 5mW then find the intensity of the laser
beam?