Find the focal length and nature of lens which should be placed in contact with a lens of focal length 10 cm so that the power of the combination becomes 5D.
Power(P2) of lens with 10 cm focal length =
Let Power of the lens is P1
Total power of combination = P1 +P2
5D= P1 + 10D
P1 = -5D
focal length =
Power of the lens is negative so the given lens is concave lens
Let Power of the lens is P1
Total power of combination = P1 +P2
5D= P1 + 10D
P1 = -5D
focal length =
Power of the lens is negative so the given lens is concave lens