Question

a convex lens is of focal length 10cm.what is its power?

Answer 1

f=10cm
so,
power = 100/f........{since, f is in cm}
           =100/10
           =10D...ans

Answer 2

f=10cm=10/100m=1/10m
p=1/f
   =+10d
 
the +ve sign coz focal length is +ve of convex lens