|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.
The cylinder contains a parabolic mirror in the back, a series of glass strips in the front, and two "carbons" in the middle.
The parabolic mirror will reflect the star to a perfect focus.
The parabolic mirror has the property of rendering parallel, or nearly so, the rays from a light-source placed at its focus.
Examine the second photograph, which shows a spherical, sound wave starting at the focus of a parabolic mirror.
Had the elevation of the parabolic mirror been a few yards higher, none could have lived to tell the tale.
Here it is reflected by a parabolic mirror which greatly amplifies the sounds.
Rays from the object fall on a parabolic mirror situated in the rear end of the tube.