AQA Physics 6.6.2.4

Uses and applications of electromagnetic waves

Every part of the electromagnetic spectrum has a job. Match each use to its wave, then explain why it suits the job.

Combined Science · Higher tier

Start here

A remote and an X-ray.

A TV remote sends an invisible signal to the television. In hospital, an X-ray machine takes a picture of a broken bone.

If you had to guess, are the two signals the same kind of wave, or different kinds?

The spectrum and its uses

One family of waves, many jobs.

All electromagnetic waves travel at the same speed through a vacuum. They differ in wavelength and frequency, and that is what makes each type suited to different uses.

Radio waves: Television and radio.
Microwaves: Satellite communications; cooking food.
Infrared: Electrical heaters; cooking food; infrared cameras.
Visible light: Fibre optic communications.
Ultraviolet: Energy efficient lamps; sun tanning.
X-rays and gamma rays: Medical imaging and treatments.

Some uses carry risks. Ultraviolet can make skin age prematurely and increases the risk of skin cancer, so sun tanning has a cost. X-rays and gamma rays are ionising radiation, which can cause the mutation of genes and cancer, so exposure is kept as low as possible.

Sort

Drop each use onto its wave.

Place every use on the part of the spectrum it uses.

Tap a card, then tap the box it belongs in. Tap a placed card to take it back.

Higher · why this wave?

Combined Higher

Each wave is chosen for how it behaves.

Microwaves for satellites: they pass through the atmosphere to and from the satellite.
Microwaves for cooking: they are absorbed by water molecules in the food, transferring energy to its thermal store. They are absorbed mostly in the outer layers; the inside heats by conduction.
Infrared for heaters and cameras: it is absorbed by surfaces, transferring energy to their thermal store; warm objects emit it, so a camera can detect them in the dark.
Ultraviolet in energy efficient lamps: a coating inside the lamp absorbs the ultraviolet and gives out visible light.
X-rays for imaging: they pass through soft tissue but are absorbed by bone, so bone shows up on the image.
Gamma rays for treatment: a focused beam carries enough energy to kill cancer cells.

Think again · imaging and treating

“Gamma rays are used to take pictures of broken bones.”

Your call

Choose

A doctor needs an image of a broken arm. Which wave is used?

Command words in this lesson

Give: One use for the wave named. A word or a phrase.
Identify: Name the wave from the use described.
Explain: Higher: say what the wave does (passes through, is absorbed) that makes it suit the job.

Key fact

Radio: TV and radio. Microwaves: satellites, cooking. Infrared: heaters, cooking, cameras. Visible: fibre optics. Ultraviolet: energy efficient lamps, sun tanning. X-rays and gamma rays: medical imaging and treatments.

Key note · AQA 6.6.2.4

Uses of electromagnetic waves

Radio waves: television and radio.
Microwaves: satellite communications, cooking food.
Infrared: electrical heaters, cooking food, infrared cameras.
Visible light: fibre optic communications.
Ultraviolet: energy efficient lamps, sun tanning (risk: premature skin ageing, skin cancer).
X-rays and gamma: medical imaging and treatment. Higher: X-rays pass through soft tissue, absorbed by bone; microwaves pass through the atmosphere.

Photograph this card. Tomorrow, cover it and say each line first.

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Connects to

Ask MrBadmus

Mixing up which wave does which job?

The spectrum is drawn in order, not to scale: real wavelengths range from kilometres to far smaller than an atom.