Electromagnetic Waves


Electromagnetic Spectrum

- the electromagnetic spectrum (in order of decreasing wavelength and increasing frequency and energy) is made up of:

    radio waves, microwaves, infrared radiation, visible light, ultraviolet waves, xrays and gamma rays

- the human eye can only detect visible light, the wavelength of visible light ranges from about 350nm to about 650nm

- electromagnetic waves transfer energy from a source to an absorber 

- the wave speed equation 

    wave speed = frequency x wavelength

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Light, Infrared, Microwaves and Radio waves

- white light contains all the colours of the visible spectrum

- infrared radiation is used for carrying signals from remote control handsets and inside optical fibres 

- microwaves are used to carry satelite TV programmes and mobile phone calls

- mobile phone radiation is microwave radiation, and is also radio waves at near- microwave frequencies

- different types of electromagnetic radiation are hazardous in different ways. microwaves and radio waves an heat the internal parts of people's bodies. infrared radiation can cause skin burns

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- radio waves of different frequencies are used for different purposes because the wavelength (and so the frequency) of waves affects:

    ...how far they can travel

    ...how much they spread

    ...how much information they can carry

- microwaves are used for satellite TV signals 

- further research is needed to evaluate whether or not mobile phones are safe to use

- carrier waves are waves that are used to carry information, they do this by varying their amplitude 

- optical fibres are very thin transparent fibres that are used to transmit communication signals by light and infrared radiation

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Ultraviolet Waves, X-rays and Gamma Rays

- ultraviolet waves have a shorter wavelength than visible light and can harm the skin and the eyes

- x-rays are used in hospitals to make X-rays images

- gamma rays are used to kill harmful bacteria in food, to sterilise surgical equipment and to kill cancer cells

- ionising radiation makes uncharged atoms become charged

- x-rays and gamma rays damage living tissue when they pass through it

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X-Rays in Medicine

- x-rays are used in hospitals:

    ...to make images of your internal body parts

    ...to destroy tumours at or near the body surface

- x-rays are ionising radiation and so can damage living tissue when they pass through it

- x-rays are absorbed more by bones and teeth than by soft tissues

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