IGCSE Physics / The electromagnetic spectrum
Uses of radio waves, microwaves and infrared
Edexcel International GCSE Physics (4PH1), chapter 11: The electromagnetic spectrum, specification point 3.12. Free lesson.
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Radio waves, microwaves and infrared have different uses because of the properties of each type of wave. Knowing the property and what it causes helps you explain why a wave is suitable for a particular job.
Radio waves carry broadcasts and communications
Radio waves are at the longest wavelength end of the electromagnetic spectrum. They can travel long distances through the air and carry information, which makes them useful for broadcasting and communication. Used for radio and television broadcasting. Used for communications such as walkie-talkies.
Microwaves heat food through water
Microwaves pass into food, reaching a few centimetres below its surface. They are absorbed by water molecules in the food. These molecules gain energy and vibrate more, so the food’s thermal store increases and it heats up.
Microwaves connect satellites
Microwaves are used for satellite links, including satellite television, because they pass through the atmosphere. This lets the signal reach a satellite and return to receivers on the ground.
Infrared warms objects and helps night vision
Heaters and grills give out infrared radiation, which is absorbed by skin and food, warming them. Warm objects such as people give out more infrared than cooler surroundings. Night vision equipment detects this radiation, so warm objects can be seen in the dark. TV remote controls use a short-range beam of infrared that you cannot see.
Explain each use with a property and its consequence
For each use in an exam answer, state the wave property and then explain what it causes. Different uses of the same wave can depend on different properties. For cooking, microwaves are absorbed by water molecules. The molecules gain energy, so the food heats up. For satellites, microwaves pass through the atmosphere. The signal reaches a satellite and returns to receivers on the ground. For night vision, warm objects give out more infrared than cooler surroundings. The equipment detects the infrared, so warm objects show up in the dark.