$A$ 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?

An object is initially at a distance of $100 \; cm$ from a plane mirror. If the mirror approaches the object at a speed of $10 \; cm/s$,then after $6 \; s$,the distance between the object and its image will be: (in $; cm$)

$A$ plane mirror rotating at an angular velocity of $3 \; rad/s$ reflects a light beam. The angular velocity of the reflected beam is ........ $rad/s$.

To obtain $3$ images using two plane mirrors, they should be placed at an angle of ....... $^o$.

$A$ small object is placed $10\, cm$ in front of a plane mirror. If you stand behind the object $30\, cm$ from the mirror and look at its image,the distance focused for your eye will be........$cm$.

An object is fixed at the bottom of a vessel and water is filled in the vessel up to a height of $10 \,cm$. $A$ plane mirror is placed at a height of $7 \,cm$ from the surface of water in such a way that its reflecting surface faces the water. The distance of the image from the mirror is (Refractive index of water,$n=1.33$). (in $\,cm$)