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 reflecting a ray of incident light is rotated through an angle $\theta$ about an axis through the point of incidence in the plane of the mirror perpendicular to the plane of incidence,then

The reflecting surface of a plane mirror is vertical. $A$ particle is projected in a vertical plane which is also perpendicular to the mirror. The initial velocity of the particle is $10 \, m/s$ and the angle of projection is $60^\circ$ with the horizontal. The point of projection is at a distance $5 \, m$ from the mirror. The particle moves towards the mirror. Just before the particle touches the mirror,the velocity of approach of the particle and its image is ...... $m/s$.

An object is placed between two plane mirrors inclined at some angle to each other. If the number of images formed is $7$, then the angle of inclination is: (in $^{\circ}$)

$A$ ball is projected from the top of a table with an initial speed $u$ at an angle of inclination $\theta$ with the horizontal. What is the motion of the image of the ball with respect to the ball?

Two plane mirrors are placed parallel to each other at a distance $L$ apart. $A$ point object $O$ is placed between them,at a distance $L/3$ from one mirror. Both mirrors form multiple images. The distance between any two images cannot be: