Question

When a lens of refractive index $\mu_1$ is placed in a liquid of refractive index $\mu_2$, the lens looks to be disappeared only if

• A. $2\mu_1 = \mu_2$
• B. $\mu_1 = \dfrac{2\mu_2}{3}$
• C. $\mu_1 = \mu_2$
• D. $\mu_1 = \dfrac{3\mu_2}{2}$

Hint:

A lens becomes optically invisible when its refractive index matches that of the surrounding medium.

Answer 1

The Correct Option is C

Step 1: Understand condition for lens visibility.
A lens produces refraction only when there is a difference between refractive indices of the lens and the surrounding medium.
Step 2: Case when lens disappears.
If refractive index of the lens equals that of the surrounding liquid, there is no refraction at the boundary.
Step 3: Final conclusion.
When $\mu_1 = \mu_2$, the lens does not bend light and hence appears invisible.