The exposure time of a camera lens at the $f/2.8$ setting is $1/200$ second. The correct time of exposure at $f/5.6$ is......$sec$

If the polarising angle of a piece of glass for green light is $54.74^o$,then the angle of minimum deviation for an equilateral prism made of the same glass is......$^o$ (Given $\tan 54.74^o = 1.414$)

$A$ movie projector forms an image $3.5 \ m$ long of an object $35 \ mm$ long. Supposing there is negligible absorption of light by the aperture,what is the ratio of the illuminance on the slide to the illuminance on the screen?

Assertion : $A$ red object appears dark in the yellow light.
Reason : The red colour is scattered less.

Three identical convex lenses each of focal length $f$ are placed in a straight line separated by a distance $f$ from each other. An object is located at $f/2$ in front of the leftmost lens. Then,

Amount of light entering into the camera depends upon