Electromagnetic Spectrum

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Radio Waves


  • Long wave radio (1-10km)

- Can be receieved halfway around the world due to diffraction

- They bend around the surfaces of the Earth, and around hills, through tunnels etc.

  • TV and FM Radio broadcasting (10cm-10m)

- To get reception, you have to be in direct sight of the transmitter

- Cannot diffract or go around hills; doesn't go far through tunnels

  • Short Wave Radio (10-100m)

- Can be receieved from a long distance

- This is due to the waves reflecting off the ionosphere - electrically charged layers in the Earth's upper atmosphere

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Satellite Communication

  • Shorter wavelengths (1-10cm)
  • Use microwaves that pass through the Earth's watery atmosphere without being absorbed
  • For a satellite TV, the signal from the transmitter is transmitted to space
  • There it is picked up on by a satellite receiver dish orbiting thousands of kilometers above the Earth
  • The signal is then transmitted back down to Earth in different directions
  • From that it is received from a satellite dish on the ground

Microwave Ovens

  • The microwaves are absorbed by the water molecules in the food
  • They penetrate a few cm into the food before being absorbed
  • The energy is then conducted or convected to other parts of the food
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Heating and monitoring temperature

  • IR = Heat radiation
  • ALL objects give off IR - The hotter the object, the more IR it gives off


  • It can be detected in the dark using night-vision equipment
  • This equipment turns it into electrical signals which is displayed on screen as a picture
  • Allows things that would be otherwise hidden in the dark, e.g. criminals, to be seen


  •  Internal heating of body tissue
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Visible light

Communication using optical fibres

  • Optical fibres carry data over long distances as pulses of light
  • Pulses of light enter a narrow core at an angle
  • They are reflected over and over against the sides of the core until they reach the other side
  • Used for telephone and broadband internet cables, medical purposes (allows you to "see inside" a body without having to operate), etc.


  • Lens - Focus visible light onto light-sensitive film or electronic sensores
  • Apeture - Controls how much light enters the camera (like the pupil of an eye)
  • Shutter speed - Determines how long the film or sensor is exposed to the light
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Fluorescent Lamps

  • UV radiation is absorbed and visible light is emitted
  • Nearly all of the UV radiation is absorbed by a phosphor coating on the inside of the glass which emits visible light instead. So it is safe to use
  • Fluorescent lights are more energy efficient than filament light bulbs


  • Skin burns/skin cancer
  • Blindness
  • Damage to surface cells
  • Cell mutations which could lead to cancer

Safety Precautions

  • Wear sunscreen with UV filters
  • Stay out of strong sunlight
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  • View internal structure of objects (like bodies)
  • Helps doctors diagnose broken bones
  • Airport security

X-RAY Images

  • X-Ray radiation is directed through the body onto a detector plate
  • They can easily pass through flesh but not through more dense materials like bones
  • This is why the brighter bits of the x-ray images are shown onscreen
  • Barium meal - some patients are ordered to drink barium sulphate which allows their intestines to show up clearly on a x-ray image


  • Cell mutation and cancer

Safety Precautions

  • Lead aprons and shields
  • Minimum exposure
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Gamma Rays

Sterilise medical equipment

  • By killing microbes
  • Better than boiling plastic instruments as they will likely become damaged due to the high temperatures

Sterilise food

  • By killing microbes
  • Keeps food fresher for longer without needing to preserve it through freezing, cooking etc.

Kill cancer cells

Dangers and safety precautions

  • Cell mutation and cancer
  • Keep in a lead-lined box
  • Wear protective gear when near it
  • Minimum exposure time
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