Solution
Given,
The distance between the plane mirror and the curved mirror (d) = 20 m,
Velocity of light (c) = 3 x 10^8 m/s,
Frequency of mirror (n) = 20 rev/s,
Angle (2θ) = ?
Now,
\(c=\frac{4\pi nd}\theta\)
Or, \(\theta=\frac{4\pi nd}c\)
Or, \(\theta=\frac{4\pi\times20\times20}{3\times10^8}=1.675\times10^{-5}\) rad
∴ θ = 9.6 x 10^-4 degree
and, 2θ = 1.92 x 10^-3 degree