Michael Newman, age 12, of Victoria, for is question:
How do TV pictures travel through the air?
Television, of course, is full of magic but perhaps the greatest wonder is the nothingness between the broadcasting station and your receiving set. The sound and pictures travel this distance on silent, invisible waves and they travel at the speed of light, which is 186,000 miles a second fast enough to whip around the equator seven times in less than one second,
When we travel across the country, we see tall television antennae and we hear tell of a mysterious coaxial cable. These are the gadgets which help to carry our TV programs from the broadcasting station to the sets in our living rooms. The programs are carried on silent, invisible waves which fan out in straight lines from the broadcasting station. These waves do not bend around the curved surface of the earth, but they can be beamed and the beam picked up by an antenna near the horizon, from which it is relayed to another end another antenna, perhaps clear across the continent. Or the broadcasting station may beam the TV waves carrying the programs into an underground cable the coaxial cable which carries the programs from coast to coast.
The carrier waves which carry the programs are radio waves, started by fast moving electrons. We call them electromagnetic waves because the fast moving electrons cause magnetism. We know a good deal about electromagnetic waves and we certainly know how to make use of them, But we have not yet learned what makes them travel as they do.
At the broadcasting station, a stream of electrons is agitated in a tall antenna. These electrons dog back and forth 176,000 times a second or more. It is their movement which sends out the fast electromagnetic waves, broadcasting them in all directions.
These waves are silent and invisible until they are picked up by a receiving set, which translates them into sound and pictures.
By themselves the TV waves carry no messages. At the broadcasting station, certain instruments are used to impress electrical impulses into the carrier waves. One machine scans the scenery 30 times a second and translates the image into countless dots of bright and faint light. These varying dots are fed into the carrier waves as weak and strong impulses, One set of carrier waves carries the electrical copy of the scenery while another is carrying an electrical copy of the sound.
Your TV set picks up the speeding carrier waves and translates what they are carrying. The electrical impulses are turned back into sounds and dots of light. The dots of weak and strong light build up the picture. As you watch, an entirely new picture is built up on the screen 30 times every second and a moving picture is relayed to you from the broadcasting station.