Physical processes are sometimes described visually by lines. Only the following can cross.

Which of the following form$(s)$ a virtual and erect image for all positions of the object?

$A$ camera lens is set at $f/2$ with an exposure time of $1/100 \ s$. If the lens is set at $f/4$,what will be the correct exposure time?

$A$ point source of light moves in a straight line parallel to a plane table. Consider a small portion of the table directly below the line of movement of the source. The illuminance $E$ at this portion varies with its distance $r$ from the source as:

Column-$I$ contains a list of mirrors and positions of an object. Match this with Column-$II$ describing the nature of the image formed.

Which of the following is $NOT$ involved in the formation of a secondary rainbow?