Lenses, refraction, the eye and cameras

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  • Refraction, Lenses, the eye and Cameras
    • Refraction
      • If a surface is transparent to waves then some or most of the waves hitting it will pass through
      • The speed of waves changes when they cross a boundary. This usually changes their direction as well.
      • the wave length slows and its wavelength decreases as it enters the perspex
        • as the wave returns to air, its speed and wavelength increase to their original values.
      • If the ray hits the block at a certain angle, the speed and wavelength changes
        • the ray is bent back to its original direction as it leaves the block
      • as the ray goes into the perspex, from the air, it is bent towards the normal. the angle of refraction is less than the angle of incidence.
        • If the ray hits the block at a certain angle, the speed and wavelength changes
          • the ray is bent back to its original direction as it leaves the block
    • Lenses
      • Convex
        • A lens that has at least one side that curves outward.
        • It causes the light to deviate inwards, bringing the rays of light onto a focus point
        • used to help short sightedness
      • Concave
        • A lens that has at least one side that curves inwards
        • Rays of light that pass through, diverge outwards,  bringing the focal point further back
        • used to help long sightedness
    • The Eye
      • Iris
        • this is responsible for controlling the amount of light that enters the eye
      • Cornea
        • protects the eye, like a window allowing you to see out
      • Retina
        • rods and cones convert the incident rays into images
      • pupil
        • this is the whole that the light enters through
      • lens
      • optic nerve
        • carries the electrical impulses sent by the retina to the brain where it converts these into images
    • Cameras
      • A camera lens, also known as a photographic lens, is an optical lens, or assembly of lenses used with the camera body and mechanism to make images of objects
      • These images can be stored digitally or stored on a digital memory card

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