Power Of A Lens

The power of a lens is:
            a measure of the ability of the lans to converge or diverge rays of light
               Formula:   1/Focal length(m)  or  P=1/f                      *f is the local length and measure in metres.          
           --The u nit of the power of lens is dioptres or D.
           --The focal length is inversely propotional to power of lens.
           --If focal length is shorter,power of lens is higher.
           --Thick lens has shorter focal length and higher power.
       a)thick lens

      
     b)thin lens