What is the principal focus of a spherical mirror?
1
It is a point from which the rays of light appear to be coming from on the principal axis of a convex mirror.
2
It is the point on the principal axis through which rays of light parallel to the principal axis pass after reflection or appear to be arising from this point on the principal axis.
3
It is the centre of a hollow sphere of which the spherical mirror is a part.
4
It is the midpoint of a spherical mirror.