It is desired to photograph the image of an object placed at a distance of $3\;m$ from a plane mirror. The camera,which is at a distance of $4.5\;m$ from the mirror,should be focused for a distance of......$m$.

The following figure shows the multiple reflection of a light ray along a glass corridor where the walls are either parallel or perpendicular to one another. If the angle of incidence at point $P$ is $30^o$,what are the angles of reflection of the light ray at points $Q, R, S$ and $T$ respectively?

$A$ mirror is inclined at an angle of $\theta$ with the horizontal. If a ray of light is incident at an angle $\theta$ with the mirror,then the reflected ray makes the following angle with the horizontal:

$A$ man of height $h$ requires a mirror to see his own complete image. The minimum height of the mirror required is:

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

If an observer is walking away from a plane mirror with a velocity of $6\;m/s$,then the velocity of the image with respect to the observer will be........$m/s$.