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Physics · Waves

Uses of electromagnetic waves

Describe practical applications of each type of electromagnetic wave and (Higher tier) explain why each is suitable.

  • 6 key terms
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Warm-up

Answer each one, then check.

  1. 1

    Name a type of EM wave.

    Show answerHide answer

    Radio, microwave, infrared, visible, ultraviolet, X-ray or gamma

  2. 2

    Which EM waves are ionising?

    Show answerHide answer

    X-rays and gamma rays (and some UV)

  3. 3

    What is a satellite?

    Show answerHide answer

    An object that orbits a planet

  4. 4

    What is fibre optics?

    Show answerHide answer

    Thin glass fibres that carry light signals

  5. 5

    What does a remote control use?

    Show answerHide answer

    Infrared

Learning Objectives

  1. 1Give uses of radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
  2. 2Give brief explanations of why each wave is suitable for its use (Higher tier).

USES OF EM WAVES

Electromagnetic waves have many practical applications. Each type is suited to its use by its wavelength and how it interacts with matter.

Radio: TV and radio. Microwaves: satellite communications, cooking. Infrared: heaters, cooking, cameras. Visible: fibre optics. Ultraviolet: lamps, tanning. X-rays and gamma rays: medical imaging and treatment.

Uses and Why They Suit

Higher tier explanations in the last column.

  • Radio waves

    Uses: Television and radio. Why suitable: Long wavelength, so they can travel long distances and diffract round obstacles

  • Microwaves

    Uses: Satellite communications; cooking. Why suitable: Pass through the atmosphere; absorbed by water molecules to heat food

  • Infrared

    Uses: Heaters, cooking, infrared cameras. Why suitable: Absorbed by surfaces, warming them; emitted by warm objects

  • Visible light

    Uses: Fibre optic communications. Why suitable: Reflects along glass fibres by total internal reflection; is not absorbed much

  • Ultraviolet

    Uses: Energy-efficient lamps; sun tanning. Why suitable: Makes a coating glow with visible light; causes skin to darken

  • X-rays

    Uses: Medical imaging. Why suitable: Pass through soft tissue but are absorbed by bone

  • Gamma rays

    Uses: Medical treatments and sterilising. Why suitable: Penetrating; ionising so they kill cells or bacteria

Why Microwaves for Satellites

Explain why microwaves are used for satellite communication.

Show the solutionHide the solution
  1. 1 Penetration They pass through the atmosphere without being absorbed or reflected much
  2. 2 Direction They can be sent in a narrow beam
  3. 3 Result Signals reach satellites and come back to Earth

AnswerMicrowaves can pass through the atmosphere to a satellite and back.

Why X-rays for Bones

Explain why X-rays are used to image broken bones.

Show the solutionHide the solution
  1. 1 Soft tissue Transmits X-rays, so they pass through to the detector
  2. 2 Bone Absorbs X-rays, leaving a shadow
  3. 3 Image The bone shows white or dark on the image

AnswerBone absorbs more X-rays than soft tissue, so it shows on the image.

Why Gamma Rays for Treatment

Explain why gamma rays can be used to treat cancer.

Show the solutionHide the solution
  1. 1 Penetrating They reach tumours inside the body
  2. 2 Ionising They damage or kill cancer cells
  3. 3 Beams Focused from several directions to limit damage to healthy cells

AnswerGamma rays penetrate and ionise, killing cancer cells.

Key Ideas

For exam answers.

  • Match

    Link the property of the wave to the use.

  • Hazard

    X-rays and gamma rays must be used carefully.

  • Energy transfer

    Microwave ovens and infrared heaters transfer energy to food or surfaces.

  • Communication

    Radio, microwaves, light carry information.

Match the Wave

Match the use to the wave: (a) cooking food quickly (b) remote control (c) checking for broken bones (d) broadcasting TV programmes (e) treating cancer (f) tanning.

1. Name the wave.

2. Say why it suits the job.

A good answer shows: (a) Microwaves (b) Infrared (c) X-rays (d) Radio waves (e) Gamma rays (f) Ultraviolet.

Can I...?

  1. 1Give uses of radio waves.
  2. 2Give uses of microwaves.
  3. 3Give uses of infrared.
  4. 4Give uses of visible light.
  5. 5Give uses of ultraviolet.
  6. 6Give uses of X-rays.
  7. 7Give uses of gamma rays.
  8. 8Explain why each is suitable.

Summary & Exam Focus

  • Radio: TV and radio.
  • Microwaves: satellites, cooking.
  • Infrared: heaters, cameras. Visible: fibre optics. UV: lamps, tanning.
  • X-rays and gamma: medical imaging and treatments.

Exam focus

State one use of infrared radiation. (1 mark) (1 marks)

Electrical heaters, cooking or infrared cameras.

Key terms

The vocabulary this lesson expects you to use. Each one is linked from the first place it appears above.

Satellite communication
Sending signals to and from satellites, using microwaves.
Fibre optics
Glass fibres that carry light signals.
Medical imaging
Making pictures of the inside of the body.
Radiotherapy
Using radiation to treat cancer.
Thermal camera
A camera that detects infrared.
Sterilise
Kill bacteria, e.g. using gamma rays.

Practice questions

Have a go at each one before you open its answer.

  1. Question 1 State 3 marks

    Give one use for each of the following types of electromagnetic wave: (a) radio waves (b) microwaves (c) X-rays.

    Show answerHide answer

    Model answer

    (a) Television or radio. (b) Satellite communications or cooking. (c) Medical imaging.

    Mark scheme

    • Radio waves use — 1 mark
    • Microwaves use — 1 mark
    • X-rays use — 1 mark
  2. Question 2 Explain 3 marks

    Explain why microwaves are used for satellite communications.

    Show answerHide answer

    Model answer

    Microwaves can pass through the Earth's atmosphere to the satellite and back without being absorbed or reflected much, and can be sent in narrow beams.

    Mark scheme

    • Pass through the atmosphere — 1 mark
    • Not absorbed or reflected much — 1 mark
    • Reach the satellite and return — 1 mark
  3. Question 3 Explain 3 marks

    X-rays are used to produce images of broken bones. Explain why X-rays are suitable for this use.

    Show answerHide answer

    Model answer

    Soft tissue transmits X-rays but bone absorbs them. Bones therefore show up on the detector as a shadow.

    Mark scheme

    • Transmitted by soft tissue — 1 mark
    • Absorbed by bone — 1 mark
    • Image shows bone — 1 mark
  4. Question 4 Explain 4 marks

    Explain why gamma rays can be used both to treat cancer and to sterilise medical equipment, and why care is needed when they are used.

    Show answerHide answer

    Model answer

    Gamma rays are penetrating and ionising, so they can kill cancer cells and bacteria. Because they can also damage healthy cells and cause mutations, exposure must be limited and shielding used.

    Mark scheme

    • Penetrating or high energy — 1 mark
    • Ionising: kills cells or bacteria — 1 mark
    • Also damages healthy cells — 1 mark
    • So precautions needed — 1 mark
  5. Question 5 State 2 marks

    Give two uses of infrared radiation.

    Show answerHide answer

    Model answer

    Any two from: electrical heaters, cooking food, infrared cameras, remote controls.

    Mark scheme

    • First use — 1 mark
    • Second use — 1 mark

Quick check

  1. Television signals use...

    1. AX-rays
    2. Bradio waves
    3. Cgamma rays
    4. Dultraviolet
    Show answerHide answer

    B: radio waves

    Long wavelength.

  2. A microwave oven uses...

    1. Aradio waves
    2. BX-rays
    3. Cmicrowaves
    4. Dgamma rays
    Show answerHide answer

    C: microwaves

    They heat water in food.

  3. Fibre optic cables carry...

    1. AX-rays
    2. Bradio waves only
    3. Cgamma rays
    4. Dvisible light
    Show answerHide answer

    D: visible light

    Light signals.

  4. X-rays show bones because bone...

    1. Aabsorbs X-rays
    2. Bemits X-rays
    3. Creflects all
    4. Dis magnetic
    Show answerHide answer

    A: absorbs X-rays

    Soft tissue transmits them.

  5. Gamma rays are used to...

    1. Aheat food
    2. Btreat cancer
    3. Ccook toast
    4. Dbroadcast radio
    Show answerHide answer

    B: treat cancer

    They kill cancer cells.

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