convex lenses

• Convex lens


  Lens that is thicker at the center than at the edges
• Convex lens


  • Refracts light
  • Central ray passes through without refraction (along principal axis)
  • Other rays refract and focus at principal focus
• Principal axis


  Center of the lens
• Principal focus


  The point where refracted rays converge
• Focal length


  Distance from center of lens to principal focus
• Constructing ray diagram for convex lens (object >2 focal lengths)

  1. Draw line from top of object through center of lens (unrefracted)

  2. Draw line from top of object parallel to principal axis (refracted through principal focus)

  3. Where the two lines meet is the top of the image
• Image formed (object >2 focal lengths)

  • Diminished
  • Inverted
  • Real
• Constructing ray diagram for convex lens (object 1-2 focal lengths)

  1. Draw line from top of object through center of lens (unrefracted)

  2. Draw line from top of object parallel to principal axis (refracted through principal focus)

  3. Where the two lines meet is the top of the image
• Image formed (object 1-2 focal lengths)

  • Magnified
  • Inverted
  • Real
• Properties of image depend on distance between object and lens