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Physics - Electromagnetic Waves

Electromagnetic waves are transverse waves, consisting of oscillating electric and magnetic fields. They have a wide range of frequencies, they can travel through most media, including vacuums, and when they are absorbed, they cause a rise in temperature.

Here are all the products of the Electromagnetic Spectrum in order of increasing photon energy from the highest to the lowest photon energy: Gamma rays, X-rays, Ultraviolet (UV) radiation, Visible light, Infrared radiation, Microwaves and Radio waves.

Gamma rays

Electromagnetic waves emitted by radioactive substances. They have the highest photon energy and have the same properties as X-rays, bur are produced in a different way.


Rays which ionize gases they pass through, they cause phosphorescence and bring about chemical changes on photographic plates.

Ultraviolet (UV) radiation

Ultraviolet radiation is emitted by the Sun, but only in small quantities reach the Earth's surface, These small quantities are vital to life, playing the key part in plant photosynthesis, but larger amounts are dangerous.

Visible light

Visible light waves are the only electromagnetic waves we can see. We see these waves as the colours of the rainbow. Each colour has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. When white light shines through a prism, the white light is broken apart into the colours of the visible light spectrum. Water vapour in the atmosphere can also break apart wavelengths creating a rainbow.

Infrared radiation

These electromagnetic waves are most commonly produced by hot objects and therefore those which are most frequently the cause of temperature rises. They can be used to form thermal images on special infra-red sensitive film, which is exposed by heat rather than light.


Microwave are very short radio waves used in radar (radio detection and ranging) to determine the position of an object by the time it takes for a reflected wave to return to the source. Microwave ovens use microwaves to cook food rapidly.

Radio Waves

Radio waves are electromagnetic waves which are produced when free electrons in radio antennae are made to oscillate by an electric field. The fact that the frequency of the oscillations is imposed by the field means that the waves occur as a regular stream, rather than randomly.

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