Explain how power of lens depends on its focal length?

Power of a lens is the degree to which a lens converges or diverges the light incident on it. Now, this convergence or divergence will depend on how much the lens is curved. We know that curvature of lens gives rise to focal length. Hence, power of a lens depends on its focal length

 

A lens which is higly curved will have less focal length and it also means that it will have high convergence or divergence of light. Similarly, a lens which is slightly curved will have more focal length and it also means that it will have less convergence or divergence to offer to the light. Therefore, power of a lens is inversely proportional to the focal length of the lens.