Q. When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index
A) Equal to that of glass
B) Less than one
C) Greater than that of glass
D) Less than that of glass
Explanation
(a) $\frac{1}{f} = \left( \frac{\mu_{g}}{\mu_{m}} - 1 \right)\left( \frac{1}{R_{1}} - \frac{1}{R_{2}} \right)$
Here $f = \infty$ So $\frac{1}{f} = 0\ \therefore\ \mu_{g} = \mu_{m}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.