$A$ plane mirror rotating at an angular velocity of $3 \; rad/s$ reflects a light beam. The angular velocity of the reflected beam is ........ $rad/s$.

$A$ ray reflected successively from two plane mirrors inclined at a certain angle undergoes a deviation of $300^o$. The number of observable images is:

Two plane mirrors are inclined at $70^{\circ}$. $A$ ray incident on one mirror at an angle $\theta$ with the surface,after reflection,falls on the second mirror and is reflected from there parallel to the first mirror. The value of $\theta$ is ......$^{\circ}$.

$A$ beam of light from a source $L$ is incident normally on a plane mirror fixed at a certain distance $x$ from the source. The beam is reflected back as a spot on a scale placed just above the source $L$. When the mirror is rotated through a small angle $\theta$,the spot of the light is found to move through a distance $y$ on the scale. The angle $\theta$ is given by

For a plane mirror,the focal length is . . . . . . $m$.

The light rays from an object have been reflected towards an observer from a standard flat mirror. The image observed by the observer is: