3.3.3Waves
Dangers of Electromagnetic Waves — Cambridge IGCSE Co-ordinated Sciences 0654 - Physics Revision Notes & Topical Questions
5 min read 10 parts Lesson 17 of 21
Part 1 of 8Why some waves are harmful
Energy
- Energy as frequency rises, the energy of electromagnetic waves rises
Ionisation
- Ionisation beyond visible light, ultraviolet, X-rays and gamma rays have enough energy to ionise atoms
Ionising scale
- Ionising scale the higher the frequency the more ionising the radiation
Effects
- Effects depend on the type of radiation and the size of the dose
Part 2 of 8Effects of each region
| Wave | Danger |
|---|---|
| Radio | No known danger |
| Microwaves | Internal heating of body cells |
| Infrared | Skin burns |
| Ultraviolet | Damage to surface cells and eyes, leading to skin cancer and eye conditions |
| X-rays and gamma rays | Mutation or damage to cells in the body |
Part 3 of 8Microwaves
Water absorption
- Water absorption certain frequencies are absorbed by water molecules, so there is a risk of internal heating
Everyday use
- Everyday use the lower-energy microwaves used for communications and mobile phones are not known to cause harm
Microwave ovens
- Microwave ovens emit large amounts of energy but metal walls and a metal grid in the door keep it inside
Part 4 of 8Ultraviolet
Nature
- Nature similar to visible light but invisible and carrying much more energy
Eyes
- Eyes high levels cause severe eye damage
Skin
- Skin kills cells or makes them malfunction, causing premature ageing and skin cancer
Part 5 of 8X-rays and gamma rays
Most ionising
- Most ionising they are the most ionising electromagnetic waves
Penetration
- Penetration they penetrate the body and cause internal damage
DNA
- DNA they can mutate DNA and cause cancer
Part 6 of 8Protection
Sunglasses
- Sunglasses good quality sunglasses absorb ultraviolet and protect the eyes
Sunscreen
- Sunscreen absorbs ultraviolet and protects the skin
Oven shielding
- Oven shielding metal walls and a metal grid in the glass door
Burns
- Burns avoid contact with hot objects and sources of strong infrared
Part 7 of 8Risk and benefit
Benefits
- X-rays and gamma rays are useful in medicine, but doses must be controlled
Non-ionising
- Non-ionising radio waves, microwaves, infrared and visible light
Ionising
- Ionising ultraviolet, X-rays and gamma rays
Part 8 of 8More from the specification
1Light speed signal transmission in optical fibres
- Light speed signal transmission in optical fibres total internal reflection guides infrared pulses at high propagation speed along glass optical fibres.
2Optical fibre
- Thin transparent strand that guides light by TIR
3Artificial satellite
- A man-made object orbiting a body in space.
4Digital signal
- Signal that has only two states, 1 and 0
5Analogue
- Instrument displaying a quantity by pointer position or liquid level on a scale.
6Satellite
- A body that orbits a larger one; the Moon is the Earth's natural satellite.
7Spectrum
- Range of colours in white light.
8Geostationary
- Orbiting with a period of 24 h above the equator, so staying above one point.
9Wavelength
- Distance between a point on one wave and the same point on the next wave
10Transmission
- Sending electricity along power cables from the power station to consumers.
11Electromagnetic spectrum
- Continuous family of waves from radio waves to gamma rays
12Analogue signal
- Signal that varies continuously and can take any value
Key terms
| Term | Meaning |
|---|---|
| Ionising radiation | Radiation with enough energy to ionise atoms |
| Dose | Amount of radiation received |
| Mutation | Change in DNA caused by radiation |
| Sunscreen | Substance that absorbs ultraviolet to protect the skin |
| Non-ionising radiation | Radiation that lacks enough energy to ionise atoms |
Avoid these mistakes
1
Saying all electromagnetic waves are equally dangerous — danger rises with frequency.
2
Saying mobile phone microwaves heat the body like an oven — their energy is very small.
3
Saying only X-rays are ionising — ultraviolet and gamma rays are too.
4
Saying radio waves are harmful — there is no known danger.
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