$A$ candle is placed at a distance of $10 \ cm$ from a plane mirror. At what distance from the mirror will the image of this candle be formed (in $cm$)?

In an astronomical telescope,how is the focal length of the objective lens compared to the focal length of the eyepiece?

If the radius of curvature of a concave mirror is $36\, cm$,what is its focal length (in $, cm$)?

Where should an object be placed in front of a concave mirror to obtain an inverted and magnified image?

$A$ ray of light $AB$ parallel to the principal axis is incident on a convex lens as shown in the figure. Copy the figure.
$(i)$ Draw the refracted ray.
$(ii)$ Name the point through which the refracted ray passes on the principal axis.

What do you understand by the terms
$(i)$ Real image?
$(ii)$ Virtual image?