Question

Show that if a ray of light is reflected successively from two mirrors inclined at an angle q, the deviation of the ray does not depend upon the angle of incidence. [5 MARKS]

Answer 1

Diagram: 2 Marks
Problem: 3 Marks

If $d_1$ and $d_2$ are the deviations suffered at $M_1$ and $M_2$ respectively.

Then $d_1$ = π – 2i and $d_2$ = π – 2i`

Total deviation d = 2π – 2(i + i`)

From triangle OAB, θ + $\frac{\pi }{2}$ - i` + $\frac{\pi }{2}$ – i = π or θ = i` + i

Therefore d = 2π - 2θ

Thus the total deviation is independent of angle of incidence.