Ask a Teacher

Search



what is the power of a concave lens of focal length 50cm ?
Here,we have a concave lens.Now the focal length of a concave lens is considered negative,so it is to be written with a minus sign.
Thus,Focal length,f = -50 cm
                                  = -50/100 m
                                  = - 0.5 m
Now, Power,P = 1/f(in metres)
                         = 1/-0.5
                         = -1 x 10/5
                         = - 2 D(or -2 dioptres)


comments powered by Disqus