Concave is an adjective used to describe a surface or shape that curves inward or has a hollow or recessed appearance. In the context of geometry or optics, a concave shape is one that curves or slopes inward, creating a depression or cavity.
For example:
Concave lens: In optics, a concave lens is thinner at the center than at the edges, causing light rays passing through it to diverge. Concave lenses are used to correct nearsightedness or to focus light in specific optical systems.
Concave mirror: A concave mirror curves inward, with the reflecting surface forming a hollow shape. Concave mirrors can converge parallel light rays to a focal point, making them useful in applications like reflecting telescopes and makeup mirrors.
Concave surface: In general terms, a concave surface refers to any surface that curves or slopes inward, creating a depression or hollow region.
The opposite of concave is convex, which describes a surface or shape that curves outward. The distinction between concave and convex is essential in various fields, including optics, geometry, and industrial design, where the characteristics of curved surfaces influence their optical properties or functional applications.