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

$A$ point source of light $S$,placed at a distance $60 \,cm$ in front of the centre of a plane mirror of width $50 \,cm$,hangs vertically on a wall. $A$ man walks in front of the mirror along a line parallel to the mirror at a distance $1.2 \,m$ from it (see in the figure). The distance between the extreme points where he can see the image of the light source in the mirror is $\ldots \ldots \ldots \,cm.$

$A$ point source of light $S$ is placed at a distance $10\,cm$ in front of the centre of a mirror of width $20\,cm$ suspended vertically on a wall. $A$ man walks with a speed $10\,cm/s$ in front of the mirror along a line parallel to the mirror at a distance $20\,cm$ from it as shown in the figure. Find the maximum time during which he can see the image of the source $S$ in the mirror. (in $,s$)

To get three images of a single object, one should have two plane mirrors at an angle of $...^\circ$.

What should be the angle between two plane mirrors so that whatever be the angle of incidence,the incident ray and the reflected ray from the two mirrors are parallel to each other (in $^o$)?

$A$ plane mirror produces a magnification of