The EM spectrum

The EM spectrum

1. the Electromagnetic spectrum is a continuous range of wavelengths. the types of radiation that occur in different parts of the spectrum have different uses and danger- depending on theyre wavelength and frequency.

2. this graph shows the waves going up from smallest to biggest

   • all of these waves travel at the same speed, which is the speed of light(300,000,000m/s)

3. waves

   • Radio waves
     • radio waves are used for broadcasting and communications- their longer wavelength means they travel further in the earths atmosphere, reflecting off hills and the upper atmosphere.
   • micro waves
     • micro waves are used for cooking food- microwaves are absorbed by water molecules causeing them to vibrate(heat up). they are also used in satelite transmissions -their wavelength penetrates our atmosphere
   • infared
     • infrared is used for heater and night vision equipment-all objects including people, give out infrared rays which can be detected even at night. its also used in tv remotes.
   • visible light
     • human vision,photography and optical fibres-its only part of the spectrum we can see.
   • ultraviolet
     • ultra violet is used in fluoresent lamps- they have chemicals inside them which absorb ultraviolet rays and convert the energy to visible light.
   • x-rays
     • X-rays are used in medical equipment-they enable us to see the internal structure of objects and materials by passing through some substances (eg body tissue) but being absorbed by others(eg bone).
   • Gamma rays
     • gamma rays are used for sterilising food and medical equipment - they are highly penetrative and can kill.

4. Hazards

   • over-exposure to certain types of electro magnetic radiation can be harmful. the higher the frequency of the radiation, the more damage it is likely to cause the body.
     • microwaves can cause internal heating of body tissues.
     • infared radiation is felt as heat and causes skin to burn.
     • X-rays damage cells causing mutations(which lead to cancer) and cell death- this is why doctors and dentists stand behind protective screens when taking lots of x rays.
     • gamma rays also damage cells causing mutations and cell death.
     • ultra violet radiation can cause skin cancer and overexposure to our eyes can cause blindness.

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