Question

The distance from earth surface to moon surface is 3.8x10⁵ km. Calculate areal spread and angular spread for a laser of wavelength 632.8 nm and aperture 0.5 mm when it reaches moon.

Answer 1

Angular Spread, $\theta=\dfrac{wavelength(\lambda)}{Aperture(a)}=\dfrac{632.8\times10^{-9}}{0.5\times10^{-3}}$

$\theta=1265.6\times10^{-6}$

Axial spread $=d\times\theta=(3.8\times10^5)\times(1265.6\times10^{-6})=480.928$