Q18. a gas laser cavity has been designed to operate at a = 0.5um with a cavity length oflm. with this set-up, the frequency is found to be larger than the desi

Q18. A gas laser cavity has been designed to operate at A = 0.5um with a cavity length oflm. With this set-up, the frequency is found to be larger than the desired frequency by 100 Hz. The change in the effective length of the cavity required to retune the laser is (a) -0.334 x10- m b) 0.334 x 10-m (c) 0.167 x 10m (d) -0.167x10- m