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 Form 4 Physics: Electromagnetic spectrum online video lessons

Unique properties of an electromagnetic spectrum

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Answer Text:
Unique properties
1. Radio waves– they are further divided into long waves (LW), medium waves (MW) and short waves (SW).
They are produced by electrical circuits called oscillators and they can be controlled accurately. They are easily diffracted by small objects like houses but not by large objects like hills.
2. Microwaves – they are produced by oscillation of charges in special aerials mounted on dishes. They are detected by special receivers which convert wave energy to sound i.e. ‘RADAR’ – Radio Detection and Raging.
3. Infra-red radiation – infraredradiations close to microwaves are thermal (produce heat) i.e. sun, fire but those closer to the visible light have no thermal properties i.e. TV remote control system. Detectors of infra-red radiation are the human skin, photographic film
etc.
4. Optical spectrum (visible light) – they form a tiny part of the electromagnetic spectrum. Sources include the sun, electricity, candles etc. these have wavelengths visible to the human eye and includes the optical spectrum (ROYGBIV). It is detected through the eyes, photographic films and
photocells.
5. Ultra-violet rays (UV) – has shorter wavelength than visible light. It is emitted by very hot objects i.e. the sun, welding machines etc. Exposure to UV rays may cause skin cancer and cataracts. They can be detected through photographic film.
6. X-rays – they have very short wavelength but are high energy waves. They are produced in X-ray tubes when high speed electrons are stopped by a metallic object. They are detected by the use of a photographic film or a fluorescent screen.
7. Gamma rays – produced by some radioactive materials when large changes of energy occur inside their nuclei. They can be detected by the use of photographic films, Geiger Muller tube or a cloud chamber.


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