Sound and light
Radio waves, microwaves, visible light and infrared can all be used for communication. You should know some typical examples of these, and associated hazards.
Visible light is the light we can see. It allows us to communicate with one another through books, hand signals and video, for example. The use of visible light needs the transmitter and receiver to be in the line of sight. But it is more secure against eavesdroppers than radio waves.
Cameras let us record still pictures and movies, and photography is an important use of visible light. Very bright light can damage our eyes – you should never look directly into the Sun.
We cannot see infrared radiation, but we can feel it as heat energy. High intensity infrared is used in heaters, toasters and grills, and it can cause burns. Infrared sensors can detect heat from the body. They are used in:
Infrared radiation is also used to transmit information from place to place, including:
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