Linear Magnification and Power of a Lens

Linear Magnification For Lens

Definition: The ratio of the size of the image formed by refraction from the lens to the size of the object, is called linear magnification produced by the lens. It is represented by the symbol m.

• The size of an image formed by a lens varies with the position of the object.
• The simplest way to compare the image with the object is by the ratio of their sizes. This ratio is the linear magnification.
• The ratio of the image size to the object size is the same as the ratio of the image distance to the object distance.
• In symbols,
  
   Power Of Lens
  
  
  Definition: It is the capacity or the ability of a lens to deviate (converge or diverge) the path of rays passing through it.
  • A lens producing more converging or more diverging, is said to have more power.
  • The power of a lens is related to its focal length, f by the equation:
    
  • The unit for power is dioptre (D).
  • The shorter the focal length, the greater the power.
  • The power for a convex lens is positive and the power for a concave lens is negative.