A light ray I is incident on a plane mirror M. The mirror is rotated in the direction as shown in the figure by an arrow at freuqency `9//pi` rps. The light reflected by the mirror is received on the wall W at a distance 10 m from the axis of rotation. When the angle of incidence becomes `37^(@)`, the speed of the sopt (a point) on the wall is

Options

A. 10 m/s
B. 1000 m/s
C. 500 m/s
D. none of these

Answer

B

Explanation

When mirror is rotated with angular speed `omega`, the reflected ray rotates with angular speed `2 omega(=36 rad//s)` speed of the spot `|(dh)/(dt)|=|d/(dt) (10 cot theta)|=|-10 cosec^(2) theta(d theta)/(dt)|=|-10/((0.6)^(2))xx36|=1000 m//s`