So, instead of using ultrasound, radio waves are used as they travel at 300,000,000 m/s. It works in the same way as sonar but with radio waves in place of ultrasound. A short pulse of radio waves ...

AMONG the facts to be explained in a satisfactory theory of the propagation of radio waves over the earth's surface are the curvature of the rays in transmission between stations far apart ...

For example, radio waves are transmitted by walls - this explains why these signals can be detected by radios inside a person’s house. However, visible light rays are absorbed by walls ...