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Lenses and the human eye

Lenses and the human eye






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    Lenses and the human eye Lenses and the human eye Presentation Transcript

    • Lenses and the Human Eye
    • Types of Lenses: double convex lens single convex lens concavo-convex lens convexo-concave lens single concave lens double concave lens
    • Thin Lens Equation: d 0 = distance of object from lens d i = distance of image from lens f = focal length of the lens
    • Remember Your Signs:
      • A concave lens will have a negative focal length
      • A convex lens will have a positive focal length
    • Remember Your Signs:
      • Image distance (d i ) is positive if the image is real and negative if the image is virtual
    • The Eye
    • The Eye
    • Rods and Cones
      • 2 types of light-sensitive cells in the retina:
        • 120 million rod cells - act as low-light sensors
        • 7 million cone cells - able to detect colour
          • - 3 types of cone cells, each sensitive to one of the three primary additive colours: red , green , and blue
    • contracted pupil dilated pupil
    • How the Eye Works
      • By changing the shape of the lens , a healthy eye is able to keep close objects in focus .
      • Light rays from distant objects enter the eye parallel to one another; those from close objects diverge .
    • Video: How the Human Eye Works http://www.youtube.com/watch?v=JadaWSDxBYk
    • Vision Problem: Myopia A nearsighted (myopic) eye focuses the light rays to a point in front of the retina Myopia can be corrected with diverging lenses
    • Vision Problem: Hyperopia A farsighted (hyperopic) eye focuses the light rays to a point behind the retina Hyperopia can be corrected with converging lenses
    • Vision Problem: Astigmatism Astigmatism is a vision problem that results from a cornea that has an irregular shape
    • Video: Laser Eye Surgery http://www.youtube.com/watch?v=0V4I2xzwGd4
    • Optical Technology Read p. 487-489 Answer questions 1-5