RADAR DETECTS A RAINDROP
It is easy to visualize how a radar set detects an airplane if you will consider how the large searchlights used in the last war spotted bombers flying over London. A narrow but intense beam of light, when it was intercepted by an airplane, illuminated the airplane sufficiently for it to be seen from the ground. When we say it could be seen, we mean that the amount of light reflected was enough to register a visible image in the human eye.
If one were using a radar set, an electromagnetic wave having a wave length much longer than that of light would be transmitted in a narrow beam, and some of the beam would be reflected back. With a searchlight beam, there would be a continuous stream of outgoing and reflected energy. In this circumstance we learn only the direction to the airplane but not the range. With a radar set, which sends out a short burst of power and measures the time for the reflected pulse to return, both direction and range may be obtained.
Whether one used radar waves or light rays would