Question

What are the advantage of parabolic reflectors over con ave reflectors?

Answer 1

Spherically shaped lenses and mirrors share a problem: their shape. Parallel light rays that bounce off the central region of a spherical mirror focus farther away than light rays that bounce off the edges. This results in many focal points, which produce a blurry image. To get a clear image, all rays need to focus at the same point.
Changing the shape of a mirror from spherical to parabolic solves the problem. All light rays focus at the same point and the resulting image is sharp and clear.