Question

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 frequency `(9)/(pi) "rev"//"sec"`,The light reflected by the mirror is received on the wall `W` at a distance `10m`from the axis of rotation .When the angle of incidence becomes `37^(@)`find the speed of the spot (a point) on the wall?

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

Answer 1

Correct Answer - B

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`