Two plane mirrors are placed at an angle of $60^\circ$. $A$ horizontal light ray is reflected by the first mirror and then by the second mirror. The total deviation will be ........... $^\circ$.

The light reflected by a plane mirror may form a real image:

By what angle should $M_2$ be rotated,so that the light ray after reflection from both mirrors becomes horizontal? (The angle of incidence at mirror $M_1$ is $40^{\circ}$ and the angle between $M_2$ and the horizontal is $25^{\circ}$ as shown in the figure.)

The focal length of a plane mirror is .......

$A$ flat mirror $M$ is arranged parallel to a wall $W$ at a distance $l$ from it. The light produced by a point source $S$ kept on the wall is reflected by the mirror and produces a light spot on the wall. The mirror moves with velocity $v$ towards the wall.

$A$ ray of light making an angle $10^o$ with the horizontal is incident on a plane mirror making an angle $\theta$ with the horizontal. What should be the value of $\theta$ so that the reflected ray goes vertically upwards?