Question

❥Why does a parabolic mirror not have spherical aberration?...​

Answer 1

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❥Why does a parabolic mirror not have spherical aberration?...

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Parabolic shape eliminates spherical aberration. 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.

Answer 2

As the diagram above shows, light from the edge of the field is focused closer to the mirror along the optical axis than is light from the center of the field. This means it is not possible to find a single point of best focus, only a point where the image is smallest but still not sharp. The simplest way to eliminate coma with a single mirror is to change the shape from spherical to parabolic. A parabolic mirror does not suffer from spherical aberration and can focus all light to a single point.