Question

If $ab$ is the wavefront in medium $1$ and $cd$ is the wavefront in medium $2$ as light travels from medium $1$ to medium $2$. Let ${\mu }_1$ and ${\mu }_2$ be the refractive indexes in medium $1$ and $2$ respectively. Choose the correct option.

• A. ${\mu }_1={\mu }_2$
• B. ${\mu }_1<{\mu }_2$
• C. ${\mu }_1>{\mu }_2$
• D. Cannot predict

Answer 1

The correct option is B ${\mu }_1<{\mu }_2$


It can be clearly seen that the wavefront travels faster in medium $1$ than in medium $2$.

If $v_1$ is the speed of light in medium $1$ and $v_2$ is the speed of light in medium $2$

Then, $v_1>v_2$

$\Rightarrow \frac{v_1}{v_2}>1$

Also, $\frac{{\mu }_2}{{\mu }_1}=\frac{v_1}{v_2}>1$

$\therefore {\mu }_2>{\mu }_1$

Hence, option $\left(\text{B}\right)$ is correct.