Question

A solider directs a laser beam on an enemy by reflecting the beam from mirror. If the mirror is rotated by an angle $\theta$, by what angle will the reflected beam rotate?

• A. $\theta /2$
• B. $\theta$
• C. $2\theta$
• D. None of these

Answer 1

The correct option is C $2\theta$

$\begin{array}{c}\text{Now incidence angle}{i}_1=1+\theta \\ i={\gamma }_1=i+\theta \end{array}$

so angle made by final reflected

ray ofter rotating mirror $=x+x^1$

$\begin{array}{c}=\dot{i}+\theta +\theta \\ =i+2\theta \end{array}$

angle rotate by reflected ray $=i+90-x$

$=2\theta (\because i=\gamma )$

so option $c$ is correct