The eye

• Contains receptors sensitive to light intensity / colours
• 1. CORNEA

  FOCUSES LIGHT RAYS

  light rays pass though transparent front of eye
• 2. LENS

  focuses light rays onto back of eye - changes shape to look at distant or close
• 3. RETINA

  Contains receptors for light intensity / colour

  • receptor cells send electrical impulses down to OPTIC NERVE to the brain
• Ciliary muscle / suspensory ligaments

  • Surround lens to contract or relax
  • when ciliary muscle contracts (outside one) the suspensory ligaments LOOSEN (inside one) so lens is THICKER and refracts light MORE STRONGLY
  • when ciliary muscle relaxes (outside one) the suspensory ligaments are PULLED TIGHT (Inside one) so lens is THIN only SLIGHTLY REFRACTING light
• Distant objects

  ciliary muscle (outside one) relaxes and suspensory ligaments (inside ones) are PULLED TIGHT so lens is THIN and light is SLIGHTLY REFRACTED
• Near object

  Ciliary muscle contracts (outside one) so suspensory ligaments loosen (inside ones) so lens is THICKER and light is refracted MORE STRONGLY
• longsight (light refracted too much BEHIND retina)

  • can focus on distant objects
  • cant see nearby objects
  • FIXED BY: GLASSES WITH CONVEX LENSES (partially focus light before it enters eye)
• Shortsight (light refracted too much INFRONT of retina)

  • can see nearby objects
  • cant see distant
  • FIXED BY: GLASSES WITH CONCAVE LENSES (partially unfocus light before it enters eye)