Devices {television}| can display pictures and sound.
parts
A glass vacuum cathode-ray tube has an electron emitter {electron gun} at pointed end and a flat front surface coated by chemicals {phosphor} that glow after being struck by electrons.
scanning
Electromagnets outside tube direct electron paths horizontally and vertically. A single electron beam moves row by row across screen and covers whole screen once every 1/30th second.
brightness
A positive electrode controls electron stream from electron gun. Beam can be more or less to make picture lighter or darker {brightness control}. Another positive electrode {contrast control} controls difference between light and dark areas.
controls
Side electromagnets can shift picture horizontally {horizontal control} or vertically {vertical control}.
synchronization
TV signals contain synchronizing signals, so TV cameras and home TVs sweep scene at same rate. TV sound is broadcast separately from picture on FM radio.
frequency
TV has higher frequencies than radio: very high frequency (VHF) or ultra high frequency (UHF).
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7-Machine-Kinds-Electronic-Light-Wave
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Date Modified: 2022.0224