Question

A biconvex lens is made of a material having refractive index 1.2 is dipped into water having refractive index 1.33 will behave like a .

• A. convergent lens
• B. diverging lens
• C. prism

Answer 1

The correct option is B diverging lens

Given:
Refractive index of medium, ${\mu }_1=1.33$
Refractive index of lens, ${\mu }_2=1.2$

Let radius of curvature of the first surface be $R$.
Then, the radius of curvature of the second surface will be $-R$.

Using Lens Maker's Formula;
$\frac{1}{f}=(\frac{{\mu }_2}{{\mu }_1}-1)(\frac{1}{R_1}-\frac{1}{R_2})$
$\frac{1}{f}=(\frac{1.2}{1.33}-1)(\frac{1}{R}+\frac{1}{R})$
$⟹f<0$
Since f is negative, parallel rays will form image to the left of the lens. Hence, it will behave as a diverging lens.