what is a focal length of plane mirror
@your friends have answered this question very well. keep it up students.
In case of convex and concave mirrors (i e spherical mirrors) , the centre of curvature is the centre of the sphere of which the mirror forms a part and the radius of curvature is the radius of the sphere of which the mirror forms a part. The focal length is half of the radius of curvature. Now , let us imagine plane mirror to be a part of a sphere with infinite radius. As a result, the focal length will be infinity.
Infinity.because the distance of object from mirror"p" and the distance from image to mirror"q" are equal,so by using formula
we can find the answer
as the image of plane mirror is virtual,so"q" is taken negative,so putting values
and any thing divided by zero is infinity.