6.2.9Waves

Applications of EM Waves — AQA GCSE Combined Science Trilogy 8464 - Physics Revision Notes & Topical Questions

5 min read 9 parts Lesson 15 of 15

📚 AQA GCSE Combined Science Trilogy 8464 - Physics Hub / Topical Revision

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Part 1 of 7Radio waves and microwaves

Radio waves have the longest wavelengths. They are used for broadcasting radio and television, and long-wave signals travel round hills and bend over the horizon by diffraction. Short-wave radio signals are reflected from the ionosphere, so can be received over long distances. Bluetooth uses short-range radio.

Microwaves pass through the atmosphere, so are used for satellite communication and mobile phone signals. They are also used in cooking: water molecules in food absorb microwave radiation and heat up. Microwaves in satellite dishes have wavelengths of a few centimetres, so the dishes can be relatively small.

Part 2 of 7Infrared and visible light

Infrared (IR) is emitted by all warm objects. Uses include grills and toasters, which heat food by absorbing it, remote controls for televisions, thermal imaging cameras that detect heat from people at night, and intruder alarms that detect the IR from a person's body. Optical fibres carry infrared pulses for telephone and internet links.

Visible light is used for vision, photography and photosynthesis, and in optical fibres for communications. Lasers for barcode scanners and surgery also use light.

Part 3 of 7Ultraviolet, X-rays and gamma rays

Ultraviolet (UV) makes certain materials fluoresce, so it is used to detect forged banknotes and in security markings, and in sunbeds. It kills bacteria and can be used to sterilise water and surgical tools.

X-rays pass through soft tissue but are absorbed by dense materials like bone and metals, so they are used for medical imaging of bones and teeth, and for security scanners at airports. High intensity X-rays can be used to treat cancer.

Gamma rays are very penetrating, so are used to sterilise medical equipment and food, as tracers in medicine, and in radiotherapy to destroy cancerous cells. Gamma radiation is detected from outside the body as it passes through the tissue.

Part 4 of 7Matching property to use

Wave	Key property	Use
Radio	Long wavelength, diffracts	Broadcasting
Microwave	Absorbed by water, passes through the atmosphere	Cooking, satellites
Infrared	Emitted by warm objects	Heaters, remote controls
Visible	Seen by eye, passes along fibres	Vision, fibre optics
UV	Causes fluorescence, kills germs	Security marks, sterilising
X-ray	Absorbed by dense materials	Medical images
Gamma	Very penetrating, ionising	Sterilising, treating cancer

Part 5 of 7Communication by optical fibre and satellites

Optical fibres rely on total internal reflection (see Total Internal Reflection) to carry light or infrared signals along thin glass fibres with little loss.

Communication by optical fibre and satellites

They are used in telephone, broadband and medical endoscopes.

Satellites receive a signal from the ground (the uplink), amplify it and send it back at a different frequency (the downlink).

Using different frequencies prevents the weak received signal from being swamped by the strong transmitted one.

Part 6 of 7Evaluating uses in exam answers

Longer questions ask you to explain why a particular radiation is suited to a job.

Evaluating uses in exam answers

A good answer states the property and then the consequence.

For example: "Infrared is used in a thermal imaging camera because all objects emit infrared radiation, and warmer objects emit more,

so the camera can form an image of a warm body against a cooler background even in the dark." Or: "X-rays are used to image bones because bone absorbs more X-rays than soft tissue,
so the detector shows a clear shadow of the bone."

Sometimes the question asks you to compare two options.

Evaluating uses in exam answers

Radio waves for broadcast need long wavelengths that can diffract around obstacles; microwaves travel in straight lines and need a clear line of sight,

which suits satellite and mobile phone links with towers or dishes.

An optical fibre has more capacity and less signal loss than a copper cable, but it is more fragile.

State the evidence and then conclude.

Remember that a given radiation may have both uses and dangers. UV helps sterilise water but can also cause skin cancer. Mention the control measure when the question asks for safe use.

Part 7 of 7Worked examples

Explain why microwaves are used for communicating with satellites but long-wave radio is not.
Why are X-ray images of bones possible?

Key terms

Term	Meaning
Fluorescence	Absorbing UV and emitting visible light
Thermal imaging	Using infrared radiation to form an image
Optical fibre	Glass fibre guiding light by total internal reflection
Satellite	Object orbiting Earth that relays signals
Radiotherapy	Using ionising radiation to treat cancer

Avoid these mistakes

Saying microwaves cook from the inside – they heat the outer layers, the heat conducts inwards.

Saying that infrared is heat itself – IR is radiation which is absorbed and then heats an object.

Confusing UV and X-rays in uses.

Using gamma rays and X-rays as if they were produced in the same way.

Saying radio waves bend because of refraction, not diffraction, over hills.

Last updated: 20 October 2026