Question

A lens made of material of Refractive index u2 is surrounded by a medium of Refractive Index u1. The focal
length f is related as

1.f∝(u2-u1)
2.f∝u1/(u2-u1)
3.f∝(u2+u1)
4.f∝u1/(u2+u1)​

Answer 1

Answer:

2

Explanation:

the answer is 2 because I think