Focal length is half the radius of the mirror.
So ##f=30//2=15cm##
With a spherical mirror this is not the focal length, as rays do not converge in one point, depending on their distance from the optical axis. But for small mirrors this will do.
Focal length is half the radius of the mirror.
So ##f=30//2=15cm##
With a spherical mirror this is not the focal length, as rays do not converge in one point, depending on their distance from the optical axis. But for small mirrors this will do.