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Key points

  • There are seven types of electromagnetic (EM) waves, which make up the electromagnetic spectrum.
  • Electromagnetic waves are transverse waves, and travel at the speed of light.
  • Different types of electromagnetic wave have different uses and dangers.
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Electromagnetic (EM) waves

There are lots of examples of around us, including light waves, radio waves and infrared radiation. These electromagnetic waves are caused by vibrating electric and magnetic fields and they are , because the vibrations of these fields are at right angles to the direction the wave travels.

Electromagnetic waves travel at an extremely high speed: the speed of light. The speed of light in a is around 300,000,000 metres per second. At that speed, light can travel 7.5 times around Earth in just one second.

A video explaining the range of the electromagnetic spectrum

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The electromagnetic spectrum

There are seven distinct groups of electromagnetic waves which make up the electromagnetic spectrum.

An image of the electromagnetic spectrum. On the left are large waves which gradually decrease in size towards the right. From left to right, the waves are labelled: Radio waves, microwaves, infrared, visible light (illustrated with the rainbow spectrum on colours), ultraviolet, x-rays, gamma rays.

A is often used to help remember the electromagnetic waves in the correct order.

This is a sentence that can remind you of the first letter of each type of wave, in order of increasing 鈥 for example:

MnemonicWave
RememberRadio waves
MyMicrowaves
InstructionsInfrared
VisibleVisible light
UsingUltraviolet
X-rayX-ray
GlassesGamma rays
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Uses of electromagnetic waves

Electromagnetic waves have a wide range of uses. The specific uses depend on the type of electromagnetic wave.

An image of a radio

Radio waves

Radio waves are used for sending radio and television signals. They are also used to control radio-controlled toys, like cars, boats and aeroplanes. We even use radio waves in astronomy, to find out about distant stars and galaxies by studying the radio waves they produce.

An image of a radio
An image of a microwave

Microwaves

As well as heating food in microwave ovens, microwaves are used for communication. For example, mobile phones, and wireless internet (Wi-Fi) devices like laptop computers all use microwaves to communicate. Microwaves are also used for sending satellite signals, eg for systems or satellite television.

An image of a microwave
An image of a hand that is red in the middle and radiates out to blue at the edges.
Image caption,
A thermogram of a hand showing the hottest and coolest parts

Infrared

Infrared (IR) waves are emitted by all warm objects, and they are used for heating and to cook food in ovens, grills and toasters. They are also used for communication, including remote controls for televisions and stereos, as well as sending internet and telephone signals along . Infrared waves can also be detected by infrared cameras, so are often used by or in police helicopters 鈥 which can detect the infrared waves emitted by people and animals.

An image of a hand that is red in the middle and radiates out to blue at the edges.
Image caption,
A thermogram of a hand showing the hottest and coolest parts
An image of a photo being taken with a camera phone.

Visible light

This is the only type of electromagnetic radiation which is visible to the human eye. As well as allowing people to see the world around them, visible light has a range of other uses, including forming images in cameras and video cameras. Concentrated visible light emitted by can be used to send internet and telephone signals along optical fibres. Lasers can even be used in surgery, and to cut materials like wood and metals in a laser cutter.

An image of a photo being taken with a camera phone.
A picture of the sun
Image caption,
In most instances, concentrated ultraviolet light is used in detection, but the main source of UV light is from the sun

Ultraviolet

Ultraviolet (UV) waves are used in to help detect forged documents, like fake banknotes, passports or driving licences. Ultraviolet waves can be by some materials, like fluorescent inks in highlighter pens, making them glow brightly. They are also used to disinfect water, by killing bacteria.

A picture of the sun
Image caption,
In most instances, concentrated ultraviolet light is used in detection, but the main source of UV light is from the sun
An image of an X-ray of a hand

X-rays

X-rays are commonly used to produce medical images of broken bones, because they can pass through body tissues but are absorbed by bones. They are used to sterilise medical equipment, killing any bacteria present before the instruments are used for surgery. X-rays are also used in airport security scanners and to detect broken pipes underground.

An image of an X-ray of a hand
A yellow warning sign with a black circle in the middle and 3 black sections radiating from it
Image caption,
Radioactive substances emit harmful gamma ray radiation

Gamma rays

Gamma rays are also used to produce medical images and to sterilise medical instruments, in a similar way to X-rays. They are also used to sterilise food, killing bacteria in fresh fruit and vegetables to increase their shelf life. Gamma rays can also be used to detect and even to treat cancer.

A yellow warning sign with a black circle in the middle and 3 black sections radiating from it
Image caption,
Radioactive substances emit harmful gamma ray radiation

A video about the uses of electromagnetic waves

Can animals detect more of the electromagnetic spectrum than humans?

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Dangers of electromagnetic waves

An image of the Sun, an x-ray of a hand and a radiation warning symbol.

Although electromagnetic waves have many uses, they can also be dangerous. Different types of EM wave can be dangerous in different ways.

Microwaves

Because microwaves have a heating effect, some powerful microwaves can be dangerous. Your microwave oven will not switch on if the door is open, to prevent the microwaves causing damage to the cells in your body by heating them.

Infrared

The heating effect of infrared waves can cause burns to your skin.

Visible light

Concentrated visible light (eg from a laser or the Sun) can cause eye damage or even blindness.

Ultraviolet

Ultraviolet (UV) radiation can cause eye damage, which is why most sunglasses can absorb UV, preventing it from reaching the eye. The intense UV emitted by the Sun is absorbed by your skin and can cause sunburn or even damage DNA in your body cells 鈥 which could lead to skin cancer.

X-rays

X-rays can also damage DNA in body cells, which could lead to cancers developing inside the body. For low levels of exposure (eg a few medical x-rays per year) this is not a significant problem, but radiographers and other people working with X-rays must take precautions to reduce this risk.

Gamma rays

Like X-rays, gamma rays can also damage DNA in your body cells which can lead to cancers developing inside the body. People working with which emit gamma rays must limit the amount of gamma they are exposed to, by wearing protective clothing and restricting the time they work near these materials.

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Wavelengths of electromagnetic waves

Each region of the electromagnetic spectrum has a range of wavelengths associated with it. The range of wavelengths affects the way each type of EM wave behaves and interacts with matter.

Wavelengths of EM waves
Figure caption,
Each region of the electromagnetic (EM) spectrum has a range of wavelengths associated with it. Radio waves have the longest wavelengths and gamma rays have the shortest wavelengths.
Image gallerySkip image gallerySlide 1 of 7, A radio, Radio waves Radio waves have the longest wavelengths of all EM waves. Radio waves have wavelengths ranging from thousands of metres down to around 30 cm. This means they can easily travel around large objects, like hills, mountains or buildings.
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Test your knowledge

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Play the Atomic Labs game! game

Try out practical experiments in this KS3 science game.

Play the Atomic Labs game!
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