Question

If a convex lens is dipped in a liquid whose refractive index is equal to the refractive index of the lens, then lens acts like a

• A. Concave lens
• B. Plane parallel glass plate
• C. Plano convex lens
• D. Plano concave lens

Answer 1

Answer: (B)

Plane parallel glass plate

By lens maker formula.

$\frac{1}{f}=(\frac{{\mu }_2}{{\mu }_1}-1)(\frac{1}{R_1}-\frac{1}{R_2})$

So, as given in problem ${\mu }_2={\mu }_1$

So, $(\frac{{\mu }_2}{{\mu }_1}-1)=0$

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

$\Rightarrow f=\infty$

So, it act as plane parallel glass because plane parallel glass has $f=\infty$.