AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER
Uses of electromagnetic waves
Waves · Lesson 9 of 12
Teacher copy - includes the notes for whoever is teaching from it.
Warm-up
Answer each one, then check.
1. Name a type of EM wave.
Radio, microwave, infrared, visible, ultraviolet, X-ray or gamma
2. Which EM waves are ionising?
X-rays and gamma rays (and some UV)
3. What is a satellite?
An object that orbits a planet
4. What is fibre optics?
Thin glass fibres that carry light signals
5. What does a remote control use?
Infrared
Learning Objectives
1. Give uses of radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
2. Give 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 of the Electromagnetic Spectrum
|
Each wave suits its use because of its wavelength and energy. |
Icons showing the uses of radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
Uses and Why They Suit
Higher tier explanations in the last column.
|
Wave |
Uses |
Why suitable |
|---|---|---|
|
Radio waves |
Television and radio |
Long wavelength, so they can travel long distances and diffract round obstacles |
|
Microwaves |
Satellite communications; cooking |
Pass through the atmosphere; absorbed by water molecules to heat food |
|
Infrared |
Heaters, cooking, infrared cameras |
Absorbed by surfaces, warming them; emitted by warm objects |
|
Visible light |
Fibre optic communications |
Reflects along glass fibres by total internal reflection; is not absorbed much |
|
Ultraviolet |
Energy-efficient lamps; sun tanning |
Makes a coating glow with visible light; causes skin to darken |
|
X-rays |
Medical imaging |
Pass through soft tissue but are absorbed by bone |
|
Gamma rays |
Medical treatments and sterilising |
Penetrating; ionising so they kill cells or bacteria |
Why Microwaves for Satellites
|
Explain why microwaves are used for satellite communication. |
1. Penetration
They pass through the atmosphere without being absorbed or reflected much
2. Direction
They can be sent in a narrow beam
3. Result
Signals reach satellites and come back to Earth
Answer: Microwaves 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. |
1. Soft tissue
Transmits X-rays, so they pass through to the detector
2. Bone
Absorbs X-rays, leaving a shadow
3. Image
The bone shows white or dark on the image
Answer: Bone 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. |
1. Penetrating
They reach tumours inside the body
2. Ionising
They damage or kill cancer cells
3. Beams
Focused from several directions to limit damage to healthy cells
Answer: Gamma 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.
Key Terms
|
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. |
Your Task: Match the Wave
10 minutes
|
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.
Note: Ask why bone shows on an X-ray image.
Can I...?
☐ Give uses of radio waves.
☐ Give uses of microwaves.
☐ Give uses of infrared.
☐ Give uses of visible light.
☐ Give uses of ultraviolet.
☐ Give uses of X-rays.
☐ Give uses of gamma rays.
☐ Explain why each is suitable.
Summary
✓ 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) Electrical heaters, cooking or infrared cameras. |
Exam Practice: Uses of electromagnetic waves
Answer all questions. Use the mark allocation as a guide to how much to write. · 16 minutes
▸ Question 1 · 3 marks · State. Give one use for each of the following types of electromagnetic wave: (a) radio waves (b) microwaves (c) X-rays.
▸ Question 2 · 3 marks · Explain. Explain why microwaves are used for satellite communications.
▸ Question 3 · 3 marks · Explain. X-rays are used to produce images of broken bones. Explain why X-rays are suitable for this use.
▸ Question 4 · 4 marks · Explain. 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.
▸ Question 5 · 2 marks · State. Give two uses of infrared radiation.
Question 1 · 3 marks · State
|
“Give one use for each of the following types of electromagnetic wave: (a) radio waves (b) microwaves (c) X-rays.” |
HOW TO ANSWER IT Command word: State. Worth 3 marks, so plan before writing.
Question 1 · mark scheme
3 marks available. Award a mark for each point made.
▸ Radio waves use. 1 mark
▸ Microwaves use. 1 mark
▸ X-rays use. 1 mark
▸ Model answer. (a) Television or radio. (b) Satellite communications or cooking. (c) Medical imaging.
Question 2 · 3 marks · Explain
|
“Explain why microwaves are used for satellite communications.” |
HOW TO ANSWER IT Command word: Explain. Worth 3 marks, so plan before writing.
Question 2 · mark scheme
3 marks available. Award a mark for each point made.
▸ Pass through the atmosphere. 1 mark
▸ Not absorbed or reflected much. 1 mark
▸ Reach the satellite and return. 1 mark
▸ 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.
Question 3 · 3 marks · Explain
|
“X-rays are used to produce images of broken bones. Explain why X-rays are suitable for this use.” |
HOW TO ANSWER IT Command word: Explain. Worth 3 marks, so plan before writing.
Question 3 · mark scheme
3 marks available. Award a mark for each point made.
▸ Transmitted by soft tissue. 1 mark
▸ Absorbed by bone. 1 mark
▸ Image shows bone. 1 mark
▸ Model answer. Soft tissue transmits X-rays but bone absorbs them. Bones therefore show up on the detector as a shadow.
Question 4 · 4 marks · Explain
|
“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.” |
HOW TO ANSWER IT Command word: Explain. Worth 4 marks, so plan before writing.
Question 4 · mark scheme
4 marks available. Award a mark for each point made.
▸ Penetrating or high energy. 1 mark
▸ Ionising: kills cells or bacteria. 1 mark
▸ Also damages healthy cells. 1 mark
▸ So precautions needed. 1 mark
▸ 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.
Question 5 · 2 marks · State
|
“Give two uses of infrared radiation.” |
HOW TO ANSWER IT Command word: State. Worth 2 marks, so plan before writing.
Question 5 · mark scheme
2 marks available. Award a mark for each point made.
▸ First use. 1 mark
▸ Second use. 1 mark
▸ Model answer. Any two from: electrical heaters, cooking food, infrared cameras, remote controls.