Correcting Vision

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  • Created by: Jasmin
  • Created on: 05-04-13 12:30
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  • Correcting Vision
    • Short Sight = diverging lens
      • Eye cannot focus on distant objects
      • Uncorrect image is formed in front of retina
        • Eyeball is too long
        • Eye lens is too powerful
      • Diverging lens put in front of eye - diverges light before it enters the eye
        • Eye lens can focus it on the retina
    • Long Sight = converging lens
      • Eye cannot focus on nearby objects
      • Uncorrected image is formed behind retina
        • Cornea and lens are too weak
        • Eyeball is too short
      • Converging lens put in front of eye
        • Light is refracted and starts to converge before it enters the eye
          • Image focused on retina
    • Comparison of eye and camera
      • TYPE OF LENS
        • Variable focus on converging lens
        • Fixed focus on converging lens
        • Ciliary muscle alters the lens thickness
        • Adjustment of lens position
      • IMAGE
        • Real, inverted, magnification less than 1
        • Light sensitive cells on the retina
        • Photographic film (CCD sensors in a digital camera)
        • Iris controls the width of the eye pupil
        • Adjustment of aperture 'stop'
    • Lasers
      • Narrow, intense beam of light
      • Can be used to vapourise some of the cornea to change its shape
        • Changes focusing ability
          • Can increase or decrease power of cornea so light can focus images properly on retina


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