When an object is placed between two parallel mirrors,the number of images formed is:

$A$ 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

$A$ light ray is incident on a plane mirror at an angle of incidence of $30^\circ$. The deviation produced by the mirror is ........$^\circ$.

Two vertical parallel mirrors $A$ and $B$ are separated by $10\,cm$. $A$ point object $O$ is placed at a distance of $2\,cm$ from mirror $A$. The distance of the second nearest image behind mirror $A$ from the mirror $A$ is $.........\,cm$.

$A$ monochromatic beam of light enters a square enclosure with mirrored interior surfaces at an angle of incidence $\theta_i(\neq 0)$ (see figure). For some value$(s)$ of $\theta_i$,the beam is reflected by every mirrored wall (other than the one with the opening) exactly once and exits the enclosure through the same hole. Which of the following statements about this beam is correct?

$A$ man runs towards a plane mirror at a speed of $15 \, m/s$. The speed of the image relative to the mirror is ...... $m/s$.