$A$ ray of light is incident on a plane mirror at an angle of $60^{\circ}$. The angle of deviation produced by the mirror is (in $^{\circ}$)

$A$ small object of size $10\, cm$ is placed in front of a plane mirror. $A$ person stands $30\, cm$ behind the object and views the image of the object. At what distance (in $cm$) from the person's eyes must the image be focused?

$A$ cubical room is formed with $6$ plane mirrors. An insect moves along the diagonal of the floor with uniform speed $v_0$. The speed of its image in two adjacent walls,parallel to the walls,is $20\sqrt{2} \ cm/s$. Then the speed of the image formed on the roof with respect to the ground is ...... $cm/s$.

When two mirrors are placed at an angle of $60^{\circ}$ to each other,how many images will be formed by them?

Two plane mirrors are inclined at $70^{\circ}$. $A$ ray incident on one mirror at an angle $\theta$ with the surface,after reflection,falls on the second mirror and is reflected from there parallel to the first mirror. The value of $\theta$ is ......$^{\circ}$.

$A$ point source of light $S$ at a distance $d$ from the screen $A$ produces light intensity $I_0$ at the centre of the screen. If a completely reflecting mirror $M$ is placed at a distance $d$ behind the source as shown in the figure,treating the object and its image as incoherent with each other,find the intensity at the centre of the screen.