magnifying glasses

• Convex lens


  Can be used as a magnifying glass
• How to construct a ray diagram for a convex lens

  1. Draw a ray from the top of the object through the center of the lens (does not change direction)

  2. Draw a ray from the top of the object parallel to the principal axis (passes through the principal focus)

  3. Extend the rays behind the lens with dotted lines to show the position of the virtual image
• Image formed by a convex lens when object is less than 1 focal length away


  • Magnified
  • Same way up as object
  • Virtual (cannot be projected on a screen)
• Magnification


  Ratio of image height to object height
• Magnification = image height / object height