sentence: Some people say that collimated light is focused at infinity.
sentences_before: Collimated light' is light whose rays are parallel, and therefore will spread slowly as it propagates. In theory,  collimated light does not disperse with distance. Really, collimated light will disperse a little as it travels over distance. Diffraction prevents scientists from creating a perfectly collimated beam with no divergence. Light can be approximately collimated by a number of processes, for instance by using a collimator.
sentences_after: So, as the distance from a point source of light increases, the spherical wavefronts become flatter and closer to plane waves, which are perfectly collimated.
concept_name: people
headings: Collimated light
categories: Optics Astronomy