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  1. 1. With your own Eyes
  2. 2. Lenses and Light <ul><li>We will find out: </li></ul><ul><li>How light travels as a ray or a wave </li></ul><ul><li>How lenses affect the way in which light travels </li></ul><ul><li>How to calculate the power and magnification of a lens </li></ul>
  3. 3. The Eye – Rods and Cones <ul><li>The eye detects light using the retina </li></ul><ul><li>The lens focuses the light rays onto the retina </li></ul><ul><li>The retina has 2 types of cell; rods and cones. </li></ul><ul><ul><li>Rods work best in dim light but cannot see colour </li></ul></ul><ul><ul><li>Cones detect colour and work best in bright light </li></ul></ul><ul><ul><li>The fovea is the point on the retina used for detail </li></ul></ul>
  4. 4. Eye Sensitivity <ul><li>The retina adapts depending on the light being received. </li></ul><ul><li>Bright light makes the rod or cone turn down the sensitivity of its neighbours </li></ul><ul><li>This is why some images appear to look odd… </li></ul>
  5. 5. Light – Wave or Ray? Light can be represented as a wave. As found in other chapters, we can also think of it as a ‘particle’ or photon. For lenses, we can also treat light as a ray.
  6. 8. Focal Length
  7. 9. Lenses and Images <ul><li>Curvature added by lens = 1/focal length (1/f) = Power in Dioptres </li></ul><ul><li>Lens Equation – 1/v = 1/u + 1/f where: </li></ul><ul><li>V = image distance </li></ul><ul><li>U = object distance </li></ul><ul><li>F = focal length </li></ul><ul><li>Magnification = v/u = Image Distance/Object Distance </li></ul>

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