Question

How is power of the lens related to its focal length?How does the sign (+) or (-) of power of a lens determine its divergent or converge action?how does the power of a lens change if its focal length is doubled

Answer 1

                      1
Power =    ----------
                focal length


Convex lens (Converging lens) - Positive power
Concave lens (Diverging lens)  - Negative power


Power is inversely proportional to the focal length. So if the focal length is doubled , the power is reduced by half.

Answer 2

Hola mate

Here is your answer -

The power of a lens is its ability to bend light – the greater the power the greater the refraction of light.

The power of a lens is also related to the focal length by the following formula:  

Power of a lens =  1 /focal length of the lens