Tuesday, January 26, 2010

The power of lenses


The power of lens is a measure of its ability to converge or diverge an incident beam of light.
It is defined as the reciprocal of the focal length, in meters .
The unit of power is m-1 or dioptre.

Optical power
(also referred to as dioptric power, refractive power, focusing power, or convergence power)
Sourse : http://en.wikipedia.org/wiki/Lens_power

Worked example :
Determine the power of each of the following lenses.
a) Convex lens, f = 10 cm,
b) Concave lens, f = 10 cm.

Solution :
a) power,P = 1/0.1
= 10 D

b) power , P = -1/0.1
= -10 D

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