Solution
Given,
The deviation of reflected ray from the original direction, 2θ = 18°
Or, θ = 9° = \(9\times\frac{\mathrm\pi}{180}\) rad,
Distance between two mirrors (d) = 10^4 m,
Frequency of rotating mirror (n) = 375 rev/s,
Velocity of light (c) = ?
We have,
\(c=\frac{4\mathrm{πnd}}\theta\)
\(=\frac{4\mathrm\pi\times375\times10^4\times180}{9\times\mathrm\pi}\)
= 3 x 10^8 m/s
Hence, velocity of light (c) = 3 x 10^8 m/s