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A thin convex lens made from crown glass

Question:

A thin convex lens made from crown glass $\left(\mu=\frac{3}{2}\right)$ has focal length $f$. When it is measured in two different liquids having refractive indices $\frac{4}{3}$ and $\frac{5}{3}$, it has the focal length $f_{1}$ and $f_{2}$ respectively. The correct relation between the focal lengths is :

1. $f_{2}>f$ and $f_{1}$ becomes negative

2. $f_{1}$ and $f_{2}$ both become negative

3. $f_{1}=f_{2} 4.$f_{1}>f$and$f_{2}\$ become negative

Correct Option: , 4

Solution: