Question

A plane mirror is in a vertical plane and is rotating about a vertical axis at 100 mm horizontal beam of light is incident on the mirror. The reflected beam will rotate at

• A. $100rpm$
• B. $141rpm$
• C. $0rpm$
• D. $200rpm$

Answer 1

Answer: (D)

$200rpm$

$\text{coneidea the ary diggam with notation of mirror-}$

$\begin{array}{c}\text{when ray hits miraon nosmally (position, ) reglected}\\ \text{say is along incident ray.}\\ \text{Now iof mirros rotate with angleq}\end{array}$

$\theta$

$\begin{array}{c}\text{of then roflected}\end{array}$

aotate with angle $2\theta$.

hence

$\begin{array}{c}{\Theta }_{RR}=2{\theta }_m\\ {\omega }_{RR}=2{\omega }_n\\ {\omega }_{RR}=200rpm\end{array}$