Electromagnetic Spectrum

Electromagnetic Spectrum

1. Radio Waves

   • Used mainly for communications
   • Long wave lenghts
   • Lowest frequency

2. Microwaves

   • Used for satellite communication and mobile phones

3. Infrared Radiation

   • Can be used to monitor temperature
     • Infrared radiation given out from hot objects
       • For example:
         • heat loss through a house's uninsulated roof
           • Can be detected using infrared sensors.
   • Optical fibres use infrared to transmit data
     • Can carry data over long distances as pulses of infrared radiation.
       • For example
         • In telephone cables
     • They work by bouncing waves off the sides of a thin core of glass or plastic.
       • The wave enters one end of the fibre and is reflected repeatedly until it merges at the other end.
   • Infrared has many uses around the home:
     • Cooking
       • Grills
       • Toasters
     • Remote controls
       • Transfer information to TV's and DVD players
     • Transmits information between:
       • Mobile Phones
       • Computers
       • Short Distances
     • Security Systems
       • Burglar alarms
       • Security lights.
       • These sensors detect heat from an intruder's body

4. Visible Light

   • We need it to see.
   • When light enters the eye, it gets refracted through the lens and focused onto the retina at the back of the eye.
     • The retina sends messages to the brain
       • Via the optic nerve
       • The brain interprets them
   • Photography works in a similar way to the eye
     • Cameras use a lense to focus visible light onto a light sensitive film that records the image
     • The lens's aperture controls how much light enters the camera.
     • By varying the aperture and shutter speed, a photographer can capture as much or as little light as they want in their photograph.
     • The shutter speed determines how long the film or sensor is exposed to the light.

5. Ultra Violet

   • Used to detect forged bank notes.
   • FLUORESCENCE is a property of certain chemicals.
     • UV radiation is absorbed
     • Visible light is emitted
       • This is why flourescent colours look so bright.
         • They actually emit light.

6. X-Rays

7. Gamma Rays