What is the mirror formula for a spherical mirror?

$A$ ray of light passing through the principal focus of a concave mirror,after reflection,travels in which direction?

Where is the image formed when an object is placed at a distance of $2f$ in front of a convex mirror?

$A$ beam of light incident on a plane mirror forms a real image on reflection. The incident beam is

$A$ concave mirror can be used to obtain a parallel beam of light from a small lamp.

The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between the lens and the image is $80 \, cm$,at what distance should the candle be placed from the lens? What is the nature of the image at a distance of $80 \, cm$ from the lens (in $, cm$)?