Spherical mirrors are of two types: concave mirrors and convex mirrors. In a concave mirror reflection of light takes place in the bent in surface or concave surface.

In case of a concave mirror, the size of image and object will be same if the object is placed at 2 f. Hence, in this case object must be place at 2 f or 2 × 15 = 30 cm.

For a flat mirror, the reflection is the same size and appears at the same distance from the mirror as the actual object. For a convex mirror the skewers pointed outward.

Newton used a concave spherical mirror to make his reflecting telescope, a design that is still popular with amateur astronomers due to its simplicity, low cost and high degree of image quality.

Concave mirrors are sort of like parabolic dishes, in that the parallel light rays bounce off the curved-in surface and bounce to the focal point, which you can picture as being where the center ...