A spherical mirror in which reflecting surface is towards the centre of the sphere of which the mirror is a part, is called concave mirror, i.e., reflection of light for this mirror occurs at concave surface or bent-in surface.
The rays of light incident on concave mirror in a direction parallel to the principal axis, actually meet at a single point F on the principal axis of the mirror. This point is called principal focus of the mirror.
Read the above passage and answer the following questions :
(i) Is principal focus of a concave mirror, a real point or a virtual point?
(ii) What happens in case of a convex mirror ?
(iii) Our teachers and parents advise us to stay focussed. What does it imply?