Uses and Dangers of EM Waves

This lesson covers the uses and dangers of each type of electromagnetic wave, as required by the AQA GCSE Physics specification (4.6.2). You need to know practical applications for each part of the EM spectrum and understand the potential harmful effects, particularly of ionising radiation.

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Radio Waves

Uses

Use	How Radio Waves Are Used
Television and radio broadcasting	Radio waves carry signals from transmitters to receivers (aerials) in homes
Communication	Two-way radios, walkie-talkies, amateur radio
Bluetooth and Wi-Fi	Short-range radio waves connect devices wirelessly
MRI scanners	Radio waves interact with hydrogen atoms in the body to produce detailed images of soft tissue

Dangers

• Radio waves are non-ionising and generally considered safe at normal exposure levels.
• There is ongoing research into whether long-term exposure to radio waves from mobile phones could affect health, but no conclusive evidence of harm has been found.

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Microwaves

Uses

Use	How Microwaves Are Used
Microwave ovens	Microwaves are absorbed by water molecules in food, causing them to vibrate faster and heat up
Satellite communication	Microwaves can pass through the atmosphere and are used to transmit signals to and from satellites
Mobile phone signals	Microwaves carry voice and data signals between phones and base stations
Radar	Microwaves are reflected by aircraft and ships, allowing their position to be detected

Dangers

• Microwaves can cause internal heating of body tissues, particularly those with high water content.
• Microwave ovens have metal casing and mesh on the door to prevent microwaves escaping.
• Prolonged exposure to high-power microwaves can cause burns to internal organs.

Exam Tip: In a microwave oven, the microwaves are absorbed by water molecules in the food, not by the plate or container. The water molecules gain kinetic energy and heat up. This is why a dry plate stays cool but the food becomes hot. This distinction is commonly tested.

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Infrared Radiation

Uses

Use	How Infrared Is Used
Heating	Electric heaters, radiators, and grills emit infrared to warm objects
Remote controls	TV remotes send coded infrared signals to the TV receiver
Thermal imaging cameras	Detect infrared emitted by objects to create heat maps (used by police, firefighters, doctors)
Optical fibre communication	Infrared signals carry data along optical fibres for internet and phone connections
Cooking	Toasters and grills cook food using infrared radiation
Security systems	Passive infrared (PIR) sensors detect body heat to trigger alarms or lights

Dangers

• Infrared radiation can cause skin burns (e.g. sunburn is partly caused by infrared).
• Prolonged exposure can cause cell damage in the skin.
• Infrared can also cause thermal damage to the eyes if intense.

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Visible Light

Uses

Use	How Visible Light Is Used
Vision	The human eye detects visible light, enabling us to see
Photography	Cameras use lenses to focus visible light onto a sensor or film
Optical fibre communication	Visible light (and infrared) carry data through optical fibres
Illumination	Light bulbs, LEDs, and fluorescent tubes provide artificial lighting
Photosynthesis	Plants absorb visible light to produce food (not a human use but biologically important)

Dangers

• Very intense visible light can cause temporary or permanent damage to the retina (e.g. looking directly at the Sun or a laser).
• Laser light is particularly dangerous because it is concentrated into a narrow, intense beam.

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Ultraviolet (UV) Radiation

Uses

Use	How UV Is Used
Fluorescent lamps	UV radiation causes a phosphor coating inside the tube to glow, producing visible light
Security marking	Invisible UV-fluorescent ink is used on banknotes and documents; visible only under UV light
Sterilisation	UV-C radiation kills bacteria and viruses; used to sterilise water and surgical equipment
Detecting forged banknotes	Genuine banknotes have UV-fluorescent features that glow under UV light
Tanning	UV radiation from the Sun or sunbeds causes melanin production in the skin

Dangers

Danger	Details
Sunburn	UV-B radiation damages skin cells, causing redness and pain
Skin cancer	Prolonged UV exposure can cause mutations in DNA, leading to skin cancer (including melanoma)
Premature skin ageing	UV-A radiation penetrates deeper into the skin and breaks down collagen
Eye damage	UV radiation can cause cataracts (clouding of the lens) and damage to the cornea (snow blindness)

Protection from UV

• Wear sun cream with a high SPF (Sun Protection Factor).
• Wear sunglasses with UV protection.
• Cover skin with clothing and wear a hat.
• Avoid prolonged exposure during the middle of the day when UV levels are highest.

Exam Tip: UV radiation is the main cause of skin cancer. In the exam, if asked about the dangers of UV, always mention skin cancer and eye damage (cataracts). For protection, mention sunscreen, sunglasses, and covering up. These are commonly tested 2-3 mark questions.

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X-rays

Uses

Use	How X-rays Are Used
Medical imaging	X-rays pass through soft tissue but are absorbed by bone, producing shadow images of the skeleton
Airport security	X-ray scanners create images of luggage contents to detect prohibited items
CT scans	Multiple X-ray images are combined by a computer to create 3D images of the body
Dental imaging	X-rays detect cavities, infections, and impacted teeth
Radiotherapy (less common; gamma more usual)	High-energy X-rays can be used to destroy cancer cells

Dangers

Danger	Details
Cell damage	X-rays are ionising and can damage or kill living cells
DNA mutations	X-rays can cause mutations in DNA, potentially leading to cancer
Risk to developing foetus	X-rays during pregnancy can harm the developing baby

Safety Precautions

• Radiographers stand behind lead-lined screens or leave the room during X-ray exposure.
• Patients wear lead aprons to protect parts of the body not being imaged.
• X-ray exposure is kept to a minimum — as low as reasonably achievable (ALARA principle).
• X-rays during pregnancy are avoided unless absolutely necessary.

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Gamma Rays

Uses

Use	How Gamma Rays Are Used
Radiotherapy	Focused beams of gamma rays destroy cancer cells (the beam is rotated around the patient to minimise damage to healthy tissue)
Sterilisation of medical equipment	Gamma rays kill bacteria on surgical instruments and syringes without the need for high temperatures
Sterilisation of food	Gamma irradiation kills bacteria in food to extend shelf life (the food does not become radioactive)
Medical tracers	A gamma-emitting radioactive tracer is injected into the patient; a gamma camera detects it to image internal organs

Dangers

Danger	Details
Cell damage and death	Gamma rays are highly penetrating and ionising; they can destroy living cells
Cancer	Gamma ray exposure can cause mutations in DNA, leading to cancer
Radiation sickness	High doses cause nausea, hair loss, organ failure, and death

Safety Precautions