Question

The focal length of a convex lens is 25cm.expess its power with sign.

Answer 1

using formula

P=1/F

HERE

F=25cm

P=?

P=1/25

P=0.04cm

P=+4m

Answer 2

given focal length of a convex lens=25 cm

power of lens= 1/focal length (in meters)

but given in cm

power of lens in cm=100/focal length

100/25=4

power of lense of convex mirror is +ve

therefore power of lens =4