Revision notes for AQA GCSE Physics Uses and applications of electromagnetic waves. Open the guide for explanations and worked examples. Written against the AQA GCSE Physics (8463) specification, so the content matches what's examinable rather than general Physics background.
Uses and applications of electromagnetic waves
What you'll learn
- The main uses of each part of the electromagnetic spectrum.
- Why different electromagnetic waves are suitable for different jobs.
- How to link a wave’s properties to applications such as communication, cooking and medical imaging.
- How to write clear Higher Tier explanations for “why this wave is used”.
Starting point: electromagnetic waves
Electromagnetic waves are a family of transverse waves. They can all travel through a vacuum, so they do not need particles to carry them from place to place.
In air or a vacuum, all electromagnetic waves travel at about the same speed:
c≈3.0×108 m/sc \approx 3.0 \times 10^8 \text{ m/s}c≈3.0×108 m/sDefinition
Electromagnetic wave
An electromagnetic wave is a transverse wave that transfers energy by oscillating electric and magnetic fields. Examples include radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
The electromagnetic spectrum is ordered by wavelength and frequency.
Definition
Wavelength and frequency
Wavelength, λ\lambdaλ, is the distance from one point on a wave to the same point on the next wave, measured in metres. Frequency, fff, is the number of waves passing a point each second, measured in hertz (Hz).
For electromagnetic waves in air:
c=fλc = f\lambdac=fλSo if the wavelength gets shorter, the frequency gets higher.
The order of the electromagnetic spectrum matters because the waves on the right have higher frequency and higher energy.
Example
Comparing wavelength and frequency
Two electromagnetic waves travel through air. Wave A has wavelength 30 m. Wave B has wavelength 0.03 m. Which has the higher frequency?
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Use the wave equation rearranged to find frequency: f=cλf = \frac{c}{\lambda}f=λc.
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For wave A: f=3.0×108 m/s30 m=1.0×107 Hzf = \frac{3.0 \times 10^8 \text{ m/s}}{30 \text{ m}} = 1.0 \times 10^7 \text{ Hz}f=30 m3.0×108 m/s=1.0×107 Hz.
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For wave B: f=3.0×108 m/s0.03 m=1.0×1010 Hzf = \frac{3.0 \times 10^8 \text{ m/s}}{0.03 \text{ m}} = 1.0 \times 10^{10} \text{ Hz}f=0.03 m3.0×108 m/s=1.0×1010 Hz.
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Wave B has the higher frequency because it has the shorter wavelength.
The key idea: match the wave to the job
Different electromagnetic waves interact with materials in different ways. A wave might be:
- transmitted — it passes through the material
- absorbed — its energy is taken in by the material
- reflected — it bounces off the material
- penetrating — it can pass through a large thickness of material
For applications, you usually explain why a wave is useful by linking its property to the job it needs to do.
Key Idea
How to explain an application
A good explanation says: what the wave needs to do, which property helps it do that, and why that property makes it suitable.
Radio waves: television and radio
Radio waves have the longest wavelengths and the lowest frequencies in the electromagnetic spectrum.
They are useful for television and radio broadcasting because they can travel long distances through the air. Their long wavelengths also allow them to diffract, meaning they spread out around obstacles such as hills and buildings.
Some radio waves can also reflect from layers high in the atmosphere, helping signals travel further around the Earth.
Definition
Diffraction
Diffraction is the spreading out of waves when they pass through a gap or around an obstacle. Longer wavelengths diffract more.
Microwaves: satellite communications and cooking food
Microwaves have shorter wavelengths than radio waves.
Satellite communications
Microwaves are used for satellite communications because they can pass through Earth’s atmosphere and can be sent in narrow beams between a dish and a satellite.
A narrow beam is useful because the signal can be aimed accurately, so less energy is wasted.
Cooking food
Microwaves are also used in microwave ovens. The microwaves are absorbed by water and fat molecules in the food. This transfers energy to the food’s internal energy store, so the temperature rises.
Common Mistake
Microwaves do not cook perfectly from the centre out
Microwaves only penetrate a few centimetres into many foods. The outer layers are heated directly by the microwaves, then energy spreads further through the food by conduction.
Example
Choosing a wave for satellite communication
A signal needs to travel from a ground station to a satellite and back to another place on Earth. Explain why microwaves are suitable.
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The signal must pass through the atmosphere, so choose a wave that is not strongly absorbed by air.
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The signal must be aimed at a satellite, so a short wavelength is useful because it can be formed into a narrow beam using a dish aerial.
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Microwaves fit both requirements: they pass through the atmosphere well and can be directed accurately, so they are suitable for satellite communication.
Infrared: heaters, cooking and cameras
Infrared radiation is emitted by warm objects. Hotter objects generally emit more infrared radiation.
Infrared is useful when energy needs to be transferred as heating.
Electrical heaters and cooking food
Infrared radiation is absorbed by the surface of objects. The absorbed energy increases the object’s internal energy store, so its temperature rises.
That is why infrared is used in:
- electrical heaters
- grills
- toasters
- some cooking appliances
Infrared cameras
Infrared cameras detect infrared radiation emitted by objects. They can form a thermal image, where hotter objects appear different from cooler objects.
This is useful for seeing warm objects in darkness, checking heat loss from buildings, and monitoring body temperature.
Key Idea
Infrared and temperature
All objects emit infrared radiation, but hotter objects emit more. Infrared cameras use this to detect temperature differences.
Visible light: fibre optic communications
Visible light is the part of the electromagnetic spectrum that human eyes can detect.
It is used in fibre optic communications. An optical fibre is a very thin strand of glass or plastic. Pulses of light travel along the fibre and carry information, such as telephone or internet data.
The light stays inside the fibre because it repeatedly reflects from the inside surface. This allows information to travel long distances with little signal loss.
Definition
Optical fibre
An optical fibre is a thin glass or plastic fibre that carries information using pulses of light.
Visible light is suitable because it can be sent as rapid pulses, and glass fibres can transmit it efficiently.
Ultraviolet: energy efficient lamps and sun tanning
Ultraviolet, often shortened to UV, has a higher frequency than visible light.
Energy efficient lamps
Some energy efficient lamps, such as fluorescent lamps, produce ultraviolet radiation inside the tube. A coating on the inside of the lamp absorbs the ultraviolet and re-emits energy as visible light.
This is more efficient than a filament lamp because less energy is wasted heating the surroundings.
Sun tanning
Ultraviolet radiation from the Sun can cause the skin to produce more melanin, which darkens the skin and produces a tan.
However, ultraviolet can also damage living cells.
Common Mistake
UV can be harmful
Ultraviolet radiation can cause sunburn and increase the risk of skin cancer. In an exam, do not describe sun tanning as automatically “safe” just because it is a use of UV.
X-rays and gamma rays: medical imaging and treatments
X-rays and gamma rays have very high frequencies and very short wavelengths. They are highly penetrating and can be ionising.
Definition
Ionising radiation
Ionising radiation has enough energy to remove electrons from atoms. This can damage living cells.
X-rays for medical imaging
X-rays are useful for imaging bones because they pass through soft tissue more easily than through bone.
- Soft tissue absorbs fewer X-rays, so more X-rays reach the detector.
- Bone absorbs more X-rays, so fewer X-rays reach the detector.
- This creates contrast on the image.
That is why X-rays are used to detect broken bones and dental problems.
Gamma rays for cancer treatment
Gamma rays can be used in radiotherapy to treat cancer. They are aimed at a tumour to kill cancer cells.
Because gamma rays are penetrating, they can reach tumours inside the body. Because they are ionising, they can damage or kill cells. Doctors aim the radiation carefully to reduce damage to healthy tissue.
Example
Explaining an X-ray image
A doctor takes an X-ray image of a patient’s arm. Explain why the bones show up clearly.
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X-rays pass through soft tissue more easily because soft tissue absorbs fewer X-rays.
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Bone is denser and absorbs more X-rays, so fewer X-rays reach the detector behind the bone.
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The detector receives different amounts of X-rays from different parts of the arm, producing contrast between bone and soft tissue.
Common Mistake
Do not just say “X-rays are strong”
For medical imaging, the important idea is different absorption: X-rays are absorbed more by bone than by soft tissue, so an image is formed.
Quick application map
You should know these main pairings:
- Radio waves — television and radio broadcasting
- Microwaves — satellite communications and cooking food
- Infrared — electrical heaters, cooking food and infrared cameras
- Visible light — fibre optic communications
- Ultraviolet — energy efficient lamps and sun tanning
- X-rays — medical imaging
- Gamma rays — cancer treatment
For Higher Tier, you may be asked to briefly explain why the wave is suitable. The best answers link the use to a property such as wavelength, absorption, transmission, penetration or ionising ability.
Exam technique
In the exam
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If the question asks for a use, give the correct wave and application pairing clearly.
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If the question asks why it is suitable, link a property to the job: for example, “microwaves pass through the atmosphere and can be directed in a narrow beam”.
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For medical uses, mention both usefulness and risk: X-rays and gamma rays are penetrating, but ionising radiation can damage cells.
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Avoid vague words like “powerful” or “strong” unless you explain the actual physics, such as absorption, penetration or frequency.
Self review
Check yourself
- Why are microwaves suitable for satellite communication?
- How does an X-ray image show bones clearly?
- Why can ultraviolet be useful in lamps but also harmful to skin?
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