Digital movie projectors work on the principle of

$A$ point object is placed mid-way between two plane mirrors at a distance $a$ apart. The plane mirrors form an infinite number of images due to multiple reflections. The distance between the $n^{th}$ order images formed in the two mirrors is

As shown in the figure,a particle is placed at $O$ in front of a plane mirror $M$. $A$ man at $P$ can move along the path $PY$ and $PY'$. Which of the following is true?

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

$A$ ray of light is incident on a plane mirror at an angle of $30^\circ$. The deviation produced in the ray is....$^\circ$.

Images formed by an object placed between two plane mirrors whose reflecting surfaces make an angle of $90^o$ with one another lie on