Question

A biconvex lens made of a transparent material of refractive index 1.25 is immersed in water of refractive index 1.33. Will the lens behave as a converging or a diverging lens? Give reason.

Answer 1

${\displaystyle \frac{1}{f}=(\mu -1)(\frac{1}{R_1}-\frac{1}{R_2})}$

${\displaystyle \frac{1}{f}=(\frac{{\mu }_m}{{\mu }_w}-1)(\frac{1}{R_1}-\frac{1}{R_2})}$

${\displaystyle \frac{{\mu }_m}{{\mu }_w}=\frac{1.25}{1.33}}$

${\displaystyle \frac{{\mu }_m}{{\mu }_w}}$ = 0.98

The value of (µ – 1) is negative and ‘f’ will be negative. So it will behave like diverging lens.