Uses and Applications of Electromagnetic Waves | Physics

📖 In-Depth Theory

Uses of Radio Waves and Microwaves

RADIO WAVES:

BROADCASTING: AM and FM radio, TV broadcasts — travel long distances, reflect off ionosphere.

COMMUNICATION: aircraft, ships, emergency services.

ASTRONOMY: radio telescopes detect radio waves from distant stars and galaxies.

MRI SCANNERS: radio waves + magnetic field → detailed images of soft tissue (no ionising radiation).

MICROWAVES:

MOBILE PHONES AND WIFI: short-range communication.

SATELLITE COMMUNICATION: microwaves pass through the atmosphere and ionosphere (radio waves reflect off ionosphere — limited for satellite use).

MICROWAVE OVENS: microwave frequency matches water molecules' resonance → absorbed → food heats from inside.

RADAR: detect aircraft, ships, weather systems — measure distance by timing reflection.

Uses of Infrared, Visible and Ultraviolet

INFRARED (IR):

HEATING: electric heaters, grills — absorbed by surfaces, converted to heat.

REMOTE CONTROLS: TV, DVD players — IR pulses carry coded signals.

FIBRE OPTICS: IR carried along optical fibres for high-speed internet.

NIGHT VISION CAMERAS: detect IR emitted by warm bodies — useful in darkness.

THERMAL IMAGING: medical, security, wildlife observation.

VISIBLE LIGHT:

PHOTOGRAPHY: cameras capture visible light.

FIBRE OPTICS: carries data as light pulses — basis of broadband internet.

PHOTOSYNTHESIS: plants absorb red and blue light.

LASERS: surgery, barcode scanners, DVD reading.

ULTRAVIOLET (UV):

STERILISATION: UV kills bacteria and viruses — used in hospitals and water treatment.

FLUORESCENCE: some materials emit visible light when absorbing UV — security markings, fluorescent lamps.

BLACK LIGHTS: detect forged bank notes (UV-reactive ink).

VITAMIN D PRODUCTION: skin produces vitamin D when exposed to UV.

Uses of X-rays and Gamma Rays

X-RAYS:

MEDICAL IMAGING: pass through soft tissue, absorbed by bone → shadow on film/detector.

CT SCANS: multiple X-ray beams → 3D image of internal structures.

AIRPORT SECURITY: luggage scanning — detect metal, explosives.

MATERIAL TESTING: checking for cracks in metal castings and welds.

GAMMA RAYS:

CANCER TREATMENT (radiotherapy): focused beams kill tumour cells.

ST ERILISATION of medical equipment: kills all microorganisms without heat.

FOOD IRRADIATION: kills bacteria in food → longer shelf life.

MEDICAL TRACERS: gamma-emitting radioisotopes injected → gamma camera detects distribution in body → reveals organ function.

THICKNESS MONITORING: detect gamma penetration through materials in manufacturing.

MATCHING APPLICATION TO WAVE TYPE:

The wave chosen matches its properties to the application:

Must penetrate enough → not be absorbed too quickly.

Must interact appropriately with the target material.

Hazard must be managed — ionising types minimised.

⚠️ Common Mistake

MRI scanners use RADIO WAVES (not X-rays) — they are safe for soft tissue imaging with no ionising radiation. X-rays are used for imaging BONE and dense structures. Also: microwaves for SATELLITE communication (pass through ionosphere); radio waves for BROADCAST (reflect off ionosphere).

📌 Key Note

Radio: broadcast, MRI. Microwave: satellites, phones, radar, cooking. IR: heating, remote controls, night vision, fibre optics. Visible: photography, fibre optics, photosynthesis. UV: sterilisation, fluorescence, vitamin D. X-ray: medical imaging, airport security, CT. Gamma: radiotherapy, sterilisation, tracers.

🎯 Matching Activity — EM Wave Applications

Match each application to the EM wave type used. — drag the symbols on the right to match the component names on the left.

Radio waves

Drop here

Microwaves

Drop here

Infrared

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X-rays

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Gamma rays

Drop here

Radiotherapy — focused beams kill cancer cells

Medical imaging of bones — absorbed by dense bone, transmitted by soft tissue

Satellite communication — passes through ionosphere to reach satellites

MRI scanner — safe for soft tissue, no ionising radiation

TV remote control — pulses of IR carry the signal to the TV

⭐ Higher Tier Only

Explain why different wavelengths of EM radiation are used for different applications in terms of their properties — penetration, absorption, reflection and refraction behaviour. Evaluate the hazards and benefits of each type in context (e.g. X-rays vs MRI vs ultrasound for medical imaging). Explain how optical fibres work using total internal reflection.

🎯 Test Yourself

Question 1 of 2

1. Why are microwaves used for satellite communications rather than radio waves?

2. UV light is used to sterilise medical equipment. Why is UV effective for this?

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⚡ Uses and Applications of Electromagnetic Waves

Uses of Radio Waves and Microwaves

Uses of Infrared, Visible and Ultraviolet

Uses of X-rays and Gamma Rays

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