$A$ watch shows time as $3:25$ when seen through a mirror,the time appeared will be

Two plane mirrors are kept on a horizontal table making an angle $\theta$ with each other as shown schematically in the figure. The angle $\theta$ is such that any ray of light reflected after striking both the mirrors returns parallel to its incident path. For this to happen,the value of $\theta$ should be (in $^{\circ}$)

$A$ wall clock has marks instead of numbers. It is placed opposite to a mirror. The time observed in the mirror reflection is $8:20$. What is the actual time on the clock?

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

Digital movie projectors work on the principle of

$A$ 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 ...... $cm/s$.