Electromagnetic Waves

Electromagnetic Waves

1. The Electromagnetic spectrum

   • Radio
     • Frequencies range 300 000 Hz to 3000 million Hz
     • We use these for radio, TV and mobile phones.
     • We uses radio waves instead of cables
     • These can be dangerous as they penetrate into our bodies and can heat the interal parts of out bodies
     • Radio waves are emitted from an aerial
     • Radio waves have different wavelengths for different purposes.
   • Microwaves
     • These are called Mircowaves as they are shorter in wavelength than radio waves.
     • We these for communication like satellite as these can pass through the atmosphere and reach to the satellite above earth. these also like radio waves carry mobile phone signals.
     • These also beam signals from one place to another as mircowaves dont spread out so much.
     • Microwaves can travel through space and ground and the signals don't weaken to much s they don't spread out.
   • Infrared
     • All objects emit Infrared, the hotter the object the more it emits.
     • Optical fibres in communication systems use this as infrared is abosorbed less than visible. Remote handsets transmits signals by infrared, when you press a button it sends out a sequence of infrared pulses.
     • Infrared scanners are used in medicine to detect hot spots on the body which mean there is unhealthy tissues.
     • You can use infrared cameras to see people and animals in the dark.
   • Light
     • light that comes from an lamp or the sun is white light this is becasue these have all the colours from the visible spectrum in it.
     • You can see the colours of the spectrum when you look at a rainbow and a glass prism of white light.
     • The wavelength increases as go from violet to red.
   • Ultraviolet radiation
     • Also know as UV
     • UV emits light that is chemical
     • Posters that glow at night is made out of UV, which contain chemicals.
     • Ultraviolet radiation is harmful to the eye can can cause blindness.
     • UV wavelength are smaller than light but carry more energy.
     • Too much UV causes sunburn and can cause skin cancer.
   • X-ray and Gamma radiation
     • They both travel into substances and may pass through them if the substance are too dense or too thick, but a thick lead would stop them
     • They are at short wavelength end of the electromagnetic and carry much more energy than longer wavelentgth electromagnetic waves.
     • But they are different from each other.

2. A long wave radio waves wavelength as long as 10 km or 10'4 and X-ray and Gamma ray have a wavelength as short as 0.0000000000001 mm or 10'-5 m

3. All Electromagnetic waves travel at the speed of 300 million m/s through space or in a vacuum, this is the distance every second.

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