What is concave mirror

Why is a concave mirror preffered to plane mirror for shaving?

A concave mirror of focal length 20 cm and a convex mirror of focal length 15 cm are placed 50 cm apart,such that the two mirrors face each other .An object is placed exactly midway betwen them.Find teh nature and position of the image formed by reflection first at the concave mirror and then at the convex mirror.

If the wavelength of incident light on a concave mirror and convex lens is increased, how will the focal length of each of these change?

Derive mirror formula for concave mirror stating assumptions?

Define the terms: concave mirror convex mirror

What happens to focal length of a concave mirror when immersed in water ?

When does a concave mirror form a vritual image?

Show that for a spherical concave mirror f=R/2 .