What is the X in X-mas?
|parabolic mirror |
A cone-shaped concave mirror with a rounded-off tip, whose cross-section is shaped like the tip of a parabola. Most of the light, radio waves, sound, and other radiation that enter the mirror straight on is reflected by the surface and converges on the focus of the parabola, where being concentrated, it can be easily detected. Conversely, radiation emanating from the focal point reflects from the inner surface of the mirror into a fairly direct beam of nearly parallel radiation that can be aimed at a target. Parabolic mirrors are the basis of parabolic antennae, as well as some megaphones and telescopic mirrors.