POWER OF LENS:We all know that what the main function of lense it is only either to converge or to diverge the rfay of light. So if the lens can converge or diverge the light more easily it means lens is more powerful. now we all know if the rays are coming from infinity they will converge at focus so if the lens is more powerful the the rays will converge very soon or u can say that the focus will be near to the lens or the lens is of small focal length. It means if the lens is of short focal length is is of more powerful. or power of the lens is inversely proportional to focal length of a lens. Means more the power of the lens less will be its focal length and hence vice a versa.


UNIT OF POWER : power of a lens is measured in Diopter.


if focal length of the lens is 1 m the the power of the lens is 1 diopter. so 1 diopter can be defined as the power of the lens whose focal length is 1 m.

power of convex lens is taken as positive and power of cancave lens is taken as negative the reason is that in convex lens rays are actually meet at focus so is has real focus but in concave lens reays are not actually meet at focus but the are appears to meet at focus so it has a virtual focus.