Question

A converging lens of refractive index $1.5$ kept in a liquid medium having the same refractive index. What would be the focal length of the lens in this medium?

• A. $f=1$
• B. $f=0$
• C. $f=\infty$
• D. Cannot be determined

Answer 1

The correct option is C $f=\infty$

We have, Len's maker formula $=\frac{1}{f}=(\frac{{\mu }_2}{{\mu }_1}-1)(\frac{1}{R_1}-\frac{1}{R_2})$,

Here, ${\mu }_1={\mu }_2=1.5$

$\Rightarrow \frac{1}{f}=0$

$\Rightarrow f=\infty$