3.3Waves
Electromagnetic Spectrum — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions
10 min read 21 parts Lesson 25 of 35 1 quiz
Lesson summary
3.3 Electromagnetic Spectrum — IGCSE PHYSICS notes: Describe the electromagnetic spectrum, its properties, uses and dangers.Order from longest wavelength — radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma raysWavelength and frequency — a long wavelengt…
- Memory aid
- Definition
- Frequency and energy
- Ionisation
- Harmful effects
- Satellites
Part 1 of 6The spectrum in order
1Order from longest wavelength
- Order from longest wavelength radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays
2Wavelength and frequency
- Wavelength and frequency a long wavelength means a low frequency and vice versa
3Visible light
- Visible light red, orange, yellow, green, blue, indigo, violet is a small part of the spectrum
4Memory aid
- Raging Martians Invaded Venus Using X-ray Guns
Part 2 of 6Properties of all electromagnetic waves
Definition
- Definition transverse waves that transfer energy from a source to an absorber
Speed
- Speed all travel at 3.0 × 108 m/s in a vacuum, about the same in air
Vacuum
- Vacuum they can travel through a vacuum
Part 3 of 6Uses
| Wave | Uses |
|---|---|
| Radio | Radio and television, astronomy, RFID |
| Microwave | Satellite television, mobile phones, Wi-Fi, microwave ovens |
| Infrared | Electric grills, remote controls, intruder alarms, thermal imaging, optical fibres |
| Visible light | Vision, photography, illumination |
| Ultraviolet | Security marking, fluorescent lamps |
| X-rays | Medical imaging of bones |
| Gamma rays | Sterilising food and equipment, detecting and treating cancer |
Part 4 of 6Dangers
Frequency and energy
- Frequency and energy energy increases with frequency
Ionisation
- Ionisation ultraviolet, X-rays and gamma rays have enough energy to ionise atoms, and the higher the frequency the more ionising
Harmful effects
- Harmful effects microwaves cause internal heating of cells, infrared causes skin burns, ultraviolet damages surface cells and eyes and can cause skin cancer, X-rays and gamma rays cause mutation or damage to cells
Radio
- Radio no known danger
Part 5 of 6Communications
Satellites
- Satellites use microwaves
Optical fibres
- Optical fibres use visible or infrared light
Signals
- Signals can be analogue or digital, and digital signals can be regenerated with little noise
Part 6 of 6More from the specification
Radiation
- Transfer by electromagnetic waves, requiring no medium
Geostationary
- Orbiting with a period of 24 h above the equator, so staying above one point.
Transmission
- Sending electricity along power cables from the power station to consumers.
Geostationary satellite
- Satellite orbiting above the equator in 24 hours at 36 000 km
Infrared radiation
- Long-wavelength thermal radiation emitted by the Earth
Artificial satellite
- A man-made object orbiting a body in space.
Key terms
| Term | Meaning |
|---|---|
| Electromagnetic wave | Transverse wave that transfers energy from a source to an absorber |
| Ionising radiation | Radiation with enough energy to remove electrons from atoms |
| Frequency | Number of waves per second, which rises from radio waves to gamma rays |
| Wavelength | Distance between waves, which falls from radio waves to gamma rays |
Avoid these mistakes
1
Saying EM waves need a medium — they travel through a vacuum.
2
Putting the spectrum in the wrong order — wavelength falls from radio waves to gamma rays.
3
Saying all EM waves are ionising — only ultraviolet and above are.
4
Saying EM waves are longitudinal — they are transverse.
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