Question

Refractive index of a transparent medium, so that it is invisible in vacuum is

• A. $1$
• B. $<1$
• C. $1.33$
• D. $>1.33$

Answer 1

The correct option is A

$1$

Step 1:Given Data and assumption

The refractive index of air, $n_a=1$

Assume, the angle of incidence is $i$.

The angle of refraction is $r$.

The refractive index of the transparent medium is $n_t$.

Step 2: Analysis:

A transparent medium is invisible in a medium if the light rays do not deviate from its path while crossing the medium.

That is,$r=i$

According to Snell’s law,

$$\begin{gathered} n_a\sin i=n_t\sin r \\ {n}_a=n_t \end{gathered}$$

Hence, the correct option is (a).