Ray Diagram

1. We can use ray diagram to determine the position and characteristic of images formed by lenses for any position of the object.
2. Ray diagram can be complete using any two out of the three rays of light.

  Rules for ray diagram:

convex lens

•  a ray of light which passes through the optical centre,O of the lens is undeviated.
• a ray  of light parallel to the principal axis is refracted and passes through the principal focus,F.
• a ray of light which passes through the principal focus,F is refracted parallel to principal axis.

concave lens

• a ray of light which passes through the optical centre,O is undeviated.
• a ray of light parallel to the principal axis is refracted and appears to come from the principal focus,F on same side of lens.
• a ray of light which travel towards the principal focus,F on the other of the lens is refracted parallel to the principal axis.

          *any two of the three rays point 1,2 and 3 are sufficient      to determine the position and characteristics of the image*