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This lesson covers the practical applications of each type of electromagnetic wave, as required by the Edexcel GCSE Combined Science specification (1SC0). You need to know the uses, explain why a particular type of EM wave is suited to each purpose, and link these to the properties of the wave.
| EM Wave | Key Uses |
|---|---|
| Radio waves | TV and radio broadcasting, communications |
| Microwaves | Cooking, satellite communication, mobile phones |
| Infrared (IR) | Heating, thermal imaging, remote controls, optical fibres |
| Visible light | Sight, photography, optical fibres, illumination |
| Ultraviolet (UV) | Fluorescent lamps, security marking, sterilisation, tanning |
| X-rays | Medical imaging, airport security, checking welds |
| Gamma rays | Cancer treatment, sterilising medical equipment, food irradiation |
Radio waves have the longest wavelengths and lowest frequencies in the EM spectrum.
| Use | How It Works |
|---|---|
| Television and radio broadcasting | Radio waves carry audio and video signals from transmitters to receivers (aerials) in homes |
| Bluetooth and Wi-Fi | Short-range radio waves link devices wirelessly |
| Communication with satellites | Longer-wavelength radio waves can diffract around obstacles and travel long distances |
Exam Tip: Diffraction is why you can still pick up a long-wave radio signal even when there are hills or buildings between you and the transmitter.
Microwaves have wavelengths between about 1 mm and 1 m.
| Use | How It Works |
|---|---|
| Microwave ovens | Microwaves are absorbed by water molecules in food, causing them to vibrate and heat up |
| Satellite communication | Microwaves pass through the atmosphere and ionosphere with little absorption, ideal for transmitting to and from satellites |
| Mobile phone networks | Microwaves carry signals between phones and base stations (masts) |
Infrared radiation is emitted by all warm objects. It has wavelengths between about 700 nm and 1 mm.
| Use | How It Works |
|---|---|
| Heating | Electric heaters, toasters and grills emit infrared to warm food or rooms |
| Thermal imaging cameras | Detect infrared emitted by objects to produce temperature maps (used by firefighters, police, building surveyors) |
| Remote controls | TV remotes send coded infrared pulses to a receiver on the TV |
| Optical fibre communication | Infrared signals carry data through optical fibres (broadband internet) |
| Night-vision equipment | Detects infrared emitted by warm bodies in darkness |
Exam Tip: Questions may ask you to explain how a thermal imaging camera works. State that all objects emit infrared radiation, and hotter objects emit more — the camera detects this and converts it into a visible image.
Visible light has wavelengths from about 400 nm (violet) to 700 nm (red).
| Use | How It Works |
|---|---|
| Sight | The human eye detects visible light reflected from objects |
| Photography | Cameras use lenses to focus visible light onto a sensor or film |
| Optical fibres | Visible light (and IR) can be sent through glass fibres using total internal reflection |
| Illumination | Lamps, LEDs, and screens produce visible light for lighting and displays |
Ultraviolet radiation has wavelengths shorter than visible light (10 nm – 400 nm).
| Use | How It Works |
|---|---|
| Fluorescent lamps | UV is produced inside the tube and causes a phosphor coating to glow, emitting visible light |
| Security marking | Special UV-sensitive inks are invisible in normal light but glow under UV (used on banknotes, stamps, passports) |
| Sterilisation / disinfection | UV-C radiation kills bacteria and viruses on surfaces and in water |
| Tanning | UV-A and UV-B from the Sun or sunbeds cause the skin to produce melanin (tan) |
Exam Tip: Be careful to distinguish between uses and dangers of UV. Tanning is a use, but excessive UV exposure causes skin cancer — you need to know both.
X-rays have very short wavelengths (0.01 nm – 10 nm) and high frequencies.
| Use | How It Works |
|---|---|
| Medical imaging (radiography) | X-rays pass through soft tissue but are absorbed by bone and metal; a detector on the other side produces an image showing bones and dense structures |
| Airport security | X-rays pass through luggage to reveal contents |
| Checking welds | X-rays can detect cracks or flaws inside metal joints |
| CT scans | Multiple X-ray images taken from different angles are combined by a computer to produce a 3D image |
Gamma rays have the shortest wavelengths and highest frequencies — and therefore the most energy.
| Use | How It Works |
|---|---|
| Cancer treatment (radiotherapy) | A focused beam of gamma rays is directed at a tumour to kill cancer cells |
| Sterilising medical equipment | Gamma rays kill bacteria on surgical instruments without heating them |
| Food irradiation | Gamma rays kill bacteria in food to extend shelf life without cooking the food |
| Medical tracers | A gamma-emitting radioactive isotope is injected and a gamma camera tracks it through the body |
Exam Tip: If asked why gamma rays are used for sterilising equipment rather than boiling, explain that gamma rays can penetrate sealed packaging and do not heat or damage the equipment.
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