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 $^o$)?

$A$ ray of light is incident normally on a plane mirror. The angle of reflection will be......$^o$

$A$ point source of light $B$ is placed at a distance $L$ in front of the centre of a mirror of width $d$ hung vertically on a wall. $A$ man walks in front of the mirror along a line parallel to the mirror at a distance $2L$ from it as shown. The greatest distance over which he can see the image of the light source in the mirror is

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 $.........\,cm$.

$A$ small plane mirror is placed at the center of a spherical screen of radius $R$. Light rays are incident on the mirror. If the mirror is rotated at a frequency of $n$ revolutions per second,what will be the speed of the reflected light spot on the screen?

When a plane mirror is placed horizontally on a level ground at a distance of $60 \ m$ from the foot of a tower,the top of the tower and its image in the mirror subtend an angle of $90^\circ$ at the eye. The height of the tower will be.....$m$.