focus

focus, in optics, the point at which rays converge after reflection by a concave mirror or refraction by a convex lens, also known as a real focus. The point from which rays appear to diverge after reflection by a convex mirror or refraction by a concave lens is known as a virtual focus. See image.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on focus from Fact Monster:

  • Cassegrain focus - Cassegrain focus: Cassegrain focus: see telescope.
  • Newtonian focus - Newtonian focus: Newtonian focus: see telescope.
  • Coudé focus - Coudé focus: Coudé focus: see telescope.
  • Hamilton, city, Bermuda - Hamilton Hamilton, city (1990 est. pop. 3,100), capital of Bermuda, on Bermuda Island. It is a port ...
  • parabola - parabola parabola , plane curve consisting of all points equidistant from a given fixed point ...

See more Encyclopedia articles on: Physics