Difference between Power of convex and concave lens
Power of convex lens
1) Power of lens is the ability to produce convergence or divergence of refracted rays.
2) Power is inversely proportional to focal length of lens. i.e. less the focal length, more is the focal length.
3) Since the focal length of convex lens is taken as positive, power of convex lens is also positive.
4) The power of convex lens is then given as,
5) SI unit of power is dioptre (D).
6) Positive power of convex lens is used for treatment of hypermetropia or far sightedness.
7) If the lens of focal length +0.50 m is required to treat hypermetropia of a person, then the power of lens will be,
Power of concave lens
1) Power of lens is the ability to produce convergence or divergence of refracted rays.
2) Power is inversely proportional to focal length of lens. i.e. less the focal length, more is the focal length.
3) Since the focal length of concave lens is taken as negative, power of concave lens is also negative.
4) The power of concave lens is then given as,
5) SI unit of power is dioptre (D).
6) Negative power of concave lens is used for treatment of myopia or near sightedness.
7) If the lens of focal length -0.25 m is required to treat myopia of a person, then the power of lens will be,