lenses

• Telescope


  Used to see distant objects
• Eyeglass


  Opticians use this to correct nearsightedness by spreading out the light before it reaches the eye, enabling you to see distant objects more clearly
• Camera


  Used to capture every moment of your life
• Flashlight


  Portable hand-held electric light, source of light when in a place with no power or during power outages
• Eyes


  Provide vision, the ability to receive and process visual detail, detect light and convert it into electro-chemical impulses in neurons
• Refraction


  The bending of a wave when it passes from one medium to another, caused by differences in density between the two substances
• The twinkling effect of stars is due to atmospheric refraction, as starlight undergoes several refractions while reaching the Earth</b>
• When light travels from air into glass, the light slows down and changes direction slightly
• When light travels from a less dense substance to a denser substance, the refracted light bends more towards the normal line
• If the light wave approaches the boundary in a perpendicular direction, the light ray doesn't refract despite the change in speed
• Laws of Refraction of Light


  • The incident ray, refracted ray, and the normal to the interface of two media at the point of incidence all lie on the same plane
  • The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant (Snell's law of refraction)
• Index of Refraction


  Describes how fast light travels through the material, calculated as the ratio between the speed of light in a vacuum (c) and the speed of light in the medium (v)
• Lens


  A curved piece of glass or other transparent material used to refract light, can have different shapes and form different types of images depending on the shape
• Types of Lenses


  • Converging lens
  • Concave lens
• Lens and Images


  1. Light rays that enter a converging lens parallel to its axis bend to meet at a point called the focal point

  2. The distance from the center of the lens to the focal point is called the focal length

  3. The optical axis usually goes through the center of the lens
• Ray Diagram for Convex Lens

  • Case 1: Beyond 2F' - Inverted, reduced, real image
  • Case 2: At 2F' - Inverted, same size, real image
  • Case 3: Between 2F' and F' - Inverted, magnified, real image
  • Case 4: At F' - No image formed
  • Case 5: Between F' and O - Upright, magnified, virtual image
• Ray Diagram for Concave Lens

  • In all locations - Upright, reduced, virtual image