Formation of Images by Lenses

 
7.1  Formation of Images by Lenses
 

1. Lens: a transparent medium such as glass which has one or two curved surfaces

2. Convex lens = converging lens:

  • biconvex
  • planoconvex
  • convex meniscus

3. Concave lens = diverging lens:

  • binconcave
  • planoconcave
  • concave meniscus

4. Determining the focal length of lens

 
 
5. Position and characteristics of images formed by a convex lens
 
Position of object Position of image  Characteristic of image
Object is further than 2F Image is between F and 2F
  • Real
  • Inverted
  • Diminised
Object is at 2F Image is at 2F
  • Real 
  • Inverted
  • Same size as object
Object is between F and 2F Image is further than 2F
  • Real
  • Inverted Magnified
Object is at F Image is at infinity
  • Virtual 
  • Upright
  • Magnified
Object is between F and optical centre Image distance is further than F
  • Virtual 
  • Upright
  • Magnified
 
6. Position and characteristics of images formed by a concave lens
 
Position of object Position of image  Characteristics of image
Object is further than 2F Between optical centre and focal point
  • Virtual
  • Upright
  • Diminised
Object is between F and optical centre Between optical centre and focal point
  • Virtual 
  • Upright
  • Diminished