Answer to Question #293506 in Optics for Chemistry

Question

The laws of optics also apply to electromagnetic waves invisible to the eye. A satellite TV

dish is used to detect radio waves coming from orbiting satellites. Why is a curved reflecting

surface (a “dish”) used? The dish is always concave, never convex; why? The actual radio receiver

is placed on an arm and suspended in front of the dish. How far in front of the dish should it be

placed?

Answer 1

Solution:

The concave surface acts as a converging mirror for the waves and focuses the light to form the desired real image at the receiver. The image of the very distinct object is at the focal point of the surface. The receiver should be at a distance f=R / 2 from the vertex of the surface.

A concave dish is used to focus the parallel rays.