Question

Find the focal length and nature of a lens which should be placed in contact with lens of focal length 10cm so that the power of combination becomes 5 diopter

Answer 1

Answer:

Explanation:

Power(P2) of lens with 10 cm focal length = 10010=10D

Let Power of the lens is P1

Total power of combination = P1 +P2

​5D=​ P1 + 10D

P1 = -5D

focal length = −15=−0.2m⇒−20 cm