Question

A laser operates at a frequency of $3\times {10}^{14}{H}_z$ and has an aperture of $1cm$. The radii spread of the beam is

• A. ${10}^{-3}$ radian
• B. $5\times {10}^{-3}$ radian
• C. ${10}^{-4}$ radian
• D. ${10}^{-2}$ radian

Answer 1

The correct option is C ${10}^{-4}$ radian

Due to non ideality in monochromatic nature of a laser, there exists some spread $\theta$,

$\theta =\frac{\lambda }{\pi r}=\frac{c}{\pi fr}$

$\theta ={10}^{-4}radian$