# Electromagnetic Wave

## Key Stage 3

### Meaning

An electromagnetic wave is a transverse wave which travels through a vacuum at 300,000,000m/s.

## Key Stage 4

### Meaning

An electromagnetic wave is a transverse wave which transfers energy by oscillating electrostatic and magnetic fields.

Electromagnetic waves are transverse because the oscillation of electrostatic and magnetic fields is perpendicular to the direction of energy transfer.
Electromagnetic waves, like all waves, carry energy and information but they do not transfer mass from one location to another.
Electromagnetic waves can pass through any transparent medium.
Electromagnetic waves do not need matter to be transmitted and can travel through a vacuum.
All electromagntic waves travel at 300,000,000m/s through a vacuum.
The properties of electromagntic waves depend on their frequency and wavelength. The lowest frequency transmits the least energy so they are the least dangerous. The highest frequency transmits the most energy so they are the most dangerous.

The electromagntic waves you should know in order from lowest frequency (longest wavelength) to highest frequency (shortest wavelength) are:

 Electromagnetic waves, are transverse with the vibration at right angles to the motion of the wave.

### Properties

NB: You do not need to remember the exact frequency or wavelength but you should remember which are highest and lowest and put them in correct order.

 Electromagntic Wave Average Frequency Average Wavelength Effect on matter Radiowaves 104Hz 103m Cause alternating currents in metals. Passes through many non-metals unaffected. Microwaves 108Hz 10-2m Cause alternating currents in metals and cause water molecules to oscillate, heating the water. Infrared 1012Hz 10-5m Causes atoms and molecules to vibrate, heating the material. Visible Light 1013Hz 10-6m Different frequencies are reflected or absorbed by different surfaces giving them colour. Ultraviolet 1016Hz 10-8m Can cause electrons in some materials to gain enough energy to leave atoms creating ions which can destroy chemical bonds. Can cause electrons in fluorescent materials to raise to a higher energy level, then as they fall to a lower energy levels the material gives off visible light. X-rays 1018Hz 10-10m Can cause electrons in many materials to gain enough energy to leave atoms creating ions which can destroy chemical bonds. However, it often passes through many non-metals without colliding with any atoms. Gamma rays 1020Hz 10-12m Causes electrons all materials to gain enough energy to leave atoms creating ions which can destroy chemical bonds. However, it passes through most materials without colliding with any atoms, unless they are particularly dense (like lead) or very thick.

### Applications

 Electromagnetic Wave Applications Radiowaves Satellite communication, radio broadcasts, television broadcasts, radar. Microwaves Satellite communication, mobile phone communication, cooking food. Infrared Remote controls, night vision, thermal imaging, cooking food, fibre optics. Visible Light Sight, photography, microscopy, telescopy, fibre optics. Ultraviolet Revealing fluorescent ink to detect forged bank notes, tanning beds, sterilising water. X-rays Medical imaging of bones. Medical imaging of intestines, using Barium Sulphate, CAT scans to identify tumours, Fluoroscopes. Gamma-rays Sterilising food, sterilising medical equipment. Irradiating cancerous tumours. Medical imaging to find blockages in organs.

### Dangers

 Electromagnetic Wave Dangers Radiowaves No dangers. Microwaves May cause internal heating. Infrared Can cause skin burns. Visible Light No dangers. Ultraviolet Can cause sunburn. Can cause skin cancer by ionising and damaging DNA molecules leading to a mutation. Can cause cataracts (clouding of the cornea). X-rays Can cause cancer anywhere in the body by ionising and damaging DNA molecules leading to a mutation. Gamma-rays Can cause cancer anywhere in the body by ionising and damaging DNA molecules leading to a mutation. Can cause radiation poisoning with high exposure.

### References

#### AQA

Electromagnetic spectrum, page 200, GCSE Combined Science Trilogy; Physics, CGP, AQA
Electromagnetic spectrum, page 223, GCSE Combined Science; The Revision Guide, CGP, AQA
Electromagnetic spectrum, page 242, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Electromagnetic spectrum, page 303, GCSE Chemistry; Student Book, Collins, AQA
Electromagnetic spectrum, page 76, GCSE Physics; The Revision Guide, CGP, AQA
Electromagnetic spectrum, pages 190-193, 196-197, GCSE Physics; Third Edition, Oxford University Press, AQA
Electromagnetic spectrum, pages 262, GCSE Combined Science Trilogy 2, Hodder, AQA
Electromagnetic waves, dangers, page 81, GCSE Physics; The Revision Guide, CGP, AQA
Electromagnetic waves, page 194, GCSE Physics, Hodder, AQA
Electromagnetic waves, pages 200-202, GCSE Combined Science Trilogy; Physics, CGP, AQA
Electromagnetic waves, pages 223, 226, 227, GCSE Combined Science; The Revision Guide, CGP, AQA
Electromagnetic waves, pages 242-244, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Electromagnetic waves, pages 262, GCSE Combined Science Trilogy 2, Hodder, AQA
Electromagnetic waves, pages 26-29, 174-179, 190-213, 238-239, GCSE Physics; Third Edition, Oxford University Press, AQA
Electromagnetic waves, pages 76, 85, GCSE Physics; The Revision Guide, CGP, AQA
Electromagnetic waves, uses, pages 224, 225, GCSE Combined Science; The Revision Guide, CGP, AQA
Electromagnetic waves, uses, pages 78-80, GCSE Physics; The Revision Guide, CGP, AQA
Electromagnetic waves; black body radiation, page 87, GCSE Physics; The Revision Guide, CGP, AQA
Electromagnetic waves; black body radiation, pages 260, 261, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Electromagnetic waves; dangers, page 228, GCSE Combined Science; The Revision Guide, CGP, AQA
Electromagnetic waves; dangers, pages 137, 139, 251, 252, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Electromagnetic waves; dangers, pages 211, 212, GCSE Combined Science Trilogy; Physics, CGP, AQA
Electromagnetic waves; hazards of, page 199, GCSE Physics, Hodder, AQA
Electromagnetic waves; Hazards of, pages 266, GCSE Combined Science Trilogy 2, Hodder, AQA
Electromagnetic waves; leslie cube investigation, page 202, GCSE Physics, Hodder, AQA
Electromagnetic waves; production and transmission of, pages 198-9, GCSE Physics, Hodder, AQA
Electromagnetic waves; Production of, pages 265-6, GCSE Combined Science Trilogy 2, Hodder, AQA
Electromagnetic waves; production, pages 201, 203, GCSE Combined Science Trilogy; Physics, CGP, AQA
Electromagnetic waves; production, pages 243, 245, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Electromagnetic waves; properties of, page 195, GCSE Physics, Hodder, AQA
Electromagnetic waves; Properties of, pages 263, GCSE Combined Science Trilogy 2, Hodder, AQA
Electromagnetic waves; refraction of, GCSE Physics, Hodder, AQA
Electromagnetic waves; refraction, pages 195-6, GCSE Physics, Hodder, AQA
Electromagnetic waves; Uses and applications of, pages 266-8, GCSE Combined Science Trilogy 2, Hodder, AQA
Electromagnetic waves; uses and applications, pages 200-1. GCSE Physics, Hodder, AQA
Electromagnetic waves; uses, pages 138, 139, 245-250, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Electromagnetic waves; uses, pages 203-208, GCSE Combined Science Trilogy; Physics, CGP, AQA

#### Edexcel

Electromagnetic radiation, page 142, GCSE Combined Science; The Revision Guide, CGP, Edexcel
Electromagnetic radiation, page 358, GCSE Combined Science, Pearson Edexcel
Electromagnetic radiation, page 92, GCSE Chemistry; The Revision Guide, CGP, Edexcel
Electromagnetic radiation, pages 94, 122, GCSE Physics, Pearson Edexcel
Electromagnetic spectrum, page 168, GCSE Combined Science; The Revision Guide, CGP, Edexcel
Electromagnetic spectrum, page 43, GCSE Physics; The Revision Guide, CGP, Edexcel
Electromagnetic spectrum, pages 344-345, GCSE Combined Science, Pearson Edexcel
Electromagnetic spectrum, pages 76-77, GCSE Physics, Pearson Edexcel

#### OCR

Electromagnetic (EM) radiation, pages 145, 192-194, 196, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR