Question

An observer $O$ is moving with the velocity $3\text{m/s}$ in the direction as shown in the figure. Find the time till the observer will be able to see his image in the plane mirror placed at an angle of ${60}^{\circ }$ with the horizontal.

• A. $2\text{sec}$
• B. $1\text{sec}$
• C. $4\text{sec}$
• D. $6\text{sec}$

Answer 1

The correct option is C $4\text{sec}$

Drawing geometry for the given condition and observing the field of view for the observer to see their image in the mirror, we have :
The distance $S$ will be the length within which observer can see his own image in the mirror.
$\Rightarrow S=6\sec {60}^{\circ }=12\text{m}$
Therefore, time for which observer can see his image is given by :
$t=\frac{S}{v}=\frac{12}{3}=4\text{sec}$