A source of laser (S), a receiver (R) and a fixed mir- ror (F) – all lie on an arc of a circle of radius `R = 0.5 km`. The distance between the source and the receiver is `d = 0.5 m`. At the centre of the circle there is a small mirror M which is rotating with angular speed `omega` (see figure). Find smallest value of `omega` is if it is seen that the source shoots a laser pulse which gets reflected at M, then gets reflected at F and finally gets reflected at M to be received by the receiver.

Answer

`150 rad s^(-1)`