refraction and the eye

• Cameras


  • Detect light
  • Use lenses to focus light
  • Contain light-sensitive material
• Human eye


  • Detect light
  • Use lenses to focus light
  • Contain light-sensitive material
• Cameras and eyes


  • Both detect light
  • Both use lenses to focus light
  • Both contain light-sensitive material
• Lens


  A specially shaped transparent object which refracts light so it focuses at a point
• Retina


  The region that makes up the back of the eye, containing light sensitive cells
• Photo-sensitive


  Materials which react or change when they absorb light
• Optic nerve


  The nerve which carries information from the eye to the brain
• How the eye 'sees'

  1. Light is focused onto the retina

  2. Photo-sensitive cells in the retina produce electrical impulses

  3. Electrical impulses are passed along the optic nerve to the brain

  4. Brain interprets the impulses as vision
• Pupil size


  • Increases in the dark to let in more light
  • Decreases in bright light
• Lens in the eye

  Can change shape to focus on objects at different distances
• Lens in a camera

  Is a fixed shape but may be adjusted to focus on objects at different distances
• Light entering the eye

  Is focused on light sensitive cells in the retina
• Light entering a camera

  Is focused onto a sensor, which produces electrical signals
• Image produced by the eye

  Is transferred as electrical signals along the optic nerve to the brain
• Image produced by a camera

  Is transferred as electrical signals to a memory card, where it is saved
• The image on the retina is upside down, but the brain flips it the right way up
• There is a blind spot in both eyes where the optic nerve joins the retina
• The brain fills in the blind spot using information from the other eye