Problem-solving approach

• A typical problem involves a system with 3 items:
  • an object,
  • a lens (with focal length f , hence focal points F)
  • an image.
• Given any 2 of these items, the position of the 3^rd item can be located by drawing any one or two of the three rays (1), (2) and (3) shown earlier.

• Principle of reversibility: You can trace light rays backwards.
• Bottom of the image on the principal axis: Location of the image.
• Image point formed from same point on object:
  • Two rays which originate from the same point will meet again at the corresponding point of the image. Always try to draw two rays from the same point on the object.