Two plane mirrors are at $45^{\circ}$ to each other. If an object is placed between them,then the number of images will be

$A$ light bulb is placed between two plane mirrors inclined at an angle of $60^{\circ}$. The number of images formed is:

$A$ clock hung on a wall has marks instead of numbers on its dial. On the opposite wall there is a mirror,and the image of the clock in the mirror,if read,indicates the time as $8:20$. What is the actual time in the clock?

$A$ light beam is being reflected by using two mirrors,as in a periscope used in submarines. If one of the mirrors rotates by an angle $\theta$,the reflected light will deviate from its original path by the angle

The focal length of a plane mirror is:

$A$ ray of light is reflected by a plane mirror. $\hat{e}_0$, $\hat{e}$ and $\hat{n}$ be the unit vectors along the incident ray, reflected ray and the normal to the reflecting surface respectively. Which of the following gives an expression for $\hat{e}$?