Two plane mirrors are at right angles to each other. $A$ man stands between them and combs his hair with his right hand. In how many of the images will he be seen using his right hand?

Two plane mirrors $AB$ and $AC$ are inclined at an angle $\theta = 20^{\circ}$. $A$ ray of light starting from point $P$ is incident at point $Q$ on the mirror $AB$,then at $R$ on mirror $AC$,and again at $S$ on $AB$. Finally,the ray $ST$ goes parallel to mirror $AC$. The angle which the ray makes with the normal at point $Q$ on mirror $AB$ is: (in $^{\circ}$)

$A$ ray of light travelling in the direction $\frac{1}{2}(\hat{i}+\sqrt{3} \hat{j})$ is incident on a plane mirror. After reflection,it travels along the direction $\frac{1}{2}(\hat{i}-\sqrt{3} \hat{j})$. The angle of incidence is: (in $^{\circ}$)

Light incident normally on a plane mirror attached to a galvanometer coil retraces its path as shown in the figure. $A$ current in the coil produces a deflection of $3.5^{\circ}$ of the mirror. What is the displacement (in $cm$) of the reflected spot of light on a screen placed $1.5\; m$ away?

$A$ man $160\,cm$ high stands in front of a plane mirror. His eyes are at a height of $150\,cm$ from the floor. The minimum length of the plane mirror required for him to see his full-length image is......$cm$.

Digital movie projectors work on the principle of