Which aberration occurs when a wide beam of light passes obliquely through a lens?

The aberration that occurs when a wide beam of light passes obliquely through a lens is known as coma. This optical phenomenon is particularly prominent in systems where the light rays entering the lens come from a point source that is not situated at the optical axis, resulting in an image that appears distorted. Coma manifests as a blurring or tailing effect, where points of light appear elongated and have a comet-like shape, particularly in the periphery of the image.

When light rays strike the lens at an angle, the lens does not focus all the rays to the same point, leading to this aberration. The severity of coma increases as the angle of incidence increases and more rays are situated away from the central axis. By understanding the nature of coma, one can take steps to mitigate its effects in optical design and imaging systems.