Uses and dangers of electromagnetic waves
Uses of EM waves
| Wave | Uses |
|---|---|
| Television and radio | |
| Satellite communications, cooking food | |
| Electric heaters, cooking food, infrared cameras | |
| Fibre optic communications | |
| Energy-efficient lamps, sun tanning | |
| Medical imaging, such as seeing broken bones | |
| Medical treatment, such as killing cancer cells; sterilising equipment |
Why each wave suits its job (Higher tier only)
| Wave | Why it suits the job |
|---|---|
| Radio | Long wavelengths travel long distances and can follow the curve of the Earth or reflect off the upper atmosphere |
| Pass through the atmosphere to reach satellites; absorbed by water molecules in food, heating it | |
| Absorbed by surfaces, heating them; warmer objects give out more, so cameras can "see" heat | |
| Travels along thin glass fibres, carrying signals | |
| Absorbed by a coating inside a lamp, which then glows with visible light | |
| Pass through soft tissue but are absorbed by bone, showing bones on an image | |
| High energy, so they kill cancer cells and bacteria |
Dangers of EM waves
, and can harm the human body. How much harm depends on the type of radiation and the dose.
- Ultraviolet makes skin age early and increases the risk of skin cancer. Sunscreen and sunglasses help.
- X-rays and gamma rays are . They can damage cells and cause in genes, which can lead to cancer.
, in , measures the risk of harm from exposure to radiation. Radiographers leave the room or stand behind lead screens when taking X-rays, to keep their dose low.