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Television waves - how they work Notes: - AM for short - a method of transmitting signals by changing amplitude of wave (must remember - amplitude = distance between two crests) - frequency of wave remains constant - at TV studio, sound is converted to electronic signals. They are then converted into electronic a pattern of changes in the amplitude of a radio wave. Your radio/ TV microphones turns it back into sound - FM for short - changing frequency of wave - have higher frequencies and more energy than AM waves - they pass through ionosphere instead of being reflected back to earth - do not travel as far as AM waves - Usually receive clearly and produce better sound quality than AM waves (well then they probably had AM waves in the 1900s) - radio waves are also used for many types of communication - FED (Federal Communications Commission). They give different radio frequencies for different uses. Radio stations are allowed to use one part of the spectrum. - AM radio stations use frequencies measured in kilohertz (kHz) (hertz= one cycle per second) - FM radio stations use frequencies measured by megahertz (MHz) - AM radio stations range from 535 kHz to 1,605 kHz
 * Inventors - Pilo T. Farnsworth (1906-1971)
 * radio sends signal (broadcast info) in air, signals carried by radio waves
 * Picture signals, also carried by radio waves
 * waves not info signals. Info 'surfs' on waves.
 * radio waves = electric and magnetic patterns
 * travels by speed of light (186,000 miles per hour)
 * camera turns pictures into signal
 * TV transmitter sends signal through air
 * TV receiver (home TV) turns it back to what you see and hear.
 * TV makes moving pictures by continuously capturing still pictures and presenting the frames no eyes so fast they look like they're moving
 * light detectors scan across picture and copy them, line by line. Turns picture into 525 different lines of colored light
 * microphones in TV studio capture the sound that goes with picture. Transmitted along pictures separately as radio signal.
 * radio waves are made of charged particles moving back and forth inside transmission antennas
 * Transmission antennas send out or broadcast radio waves everywhere. They carry info from antenna of studio to receiving antenna.
 * the two methods of transmitting signals, amplitude modulation and frequency modulation
 * Amplitude Modulation
 * Frequency modulation:
 * The Radio Spectrum

How does a television work? When a camera man films the news, the camera only takes pictures of every single movement on stage. It does that by having light detectors scan the picture line by line, and copy them. The light detectors turn picture into 525 different lines of colored light. Then it turns the pictures into a signal. When the picture is taken, the camera's antenna sends a signal (the broadcast information) in the air, and they are carried by radio waves, which are electric and magnetic patterns that are all around you that travel by the speed of light (18,600 miles per hour). The pictures sort of 'surf' on the wave. The wave goes straight into the antenna of the TV in your own home, and then the TV turns the signal back into pictures. It makes the pictures appear so fast on the screen that it looks like the people are moving. Then, back at the Studio, or broadcast station, the microphones capture the sound that goes along with the video. It is then turned into electronic signals, and sent through the air to travel on the radio waves alongside the video. Then, it is received by the TV antenna and converted back into sound.

The Effects on Television Radio waves on our health? The only known effect of radio waves - at the frequencies we use - is the so-called 'heating effect'. It is the only known effect that effects the skin tissue of human skin. That is when radio waves from a very powerful radio source - in this case, a TV transmitter - heats up human tissue if placed too close. This is caused by the ability of radio waves to make molecules vibrate more actively - a quality which was discovered in World War Two during research into radar. Research has showed that you have to be about 2 ft (0.5 m) to suffer the heating effect, though in more cautious cases, the distance is said to be 11 yards (10 m), depending on the size and output.To solve this problem, the transmitters are put in high and uneasily accessible places. Thanks to this solution, people can no longer suffer the heating effect, less possible even, to than to get burned by the bulb on a street lamp.

http://www1.orange.co.uk/about/phone_masts/faqs.html#science2