Question

A monochromatic beam of light is travelling from medium $A$ of refractive index $n_1$ to a medium $B$ of refractive index $n_2$. In the medium $A$, there are $x$ number of waves in certain distance. In the medium $B$, there are $y$ number of waves in the same distance. Then, refractive index of medium $A$ with respect to medium $B$ is

• A. $\frac {y}{x}$
• B. $\sqrt{\frac{x}{y}}$
• C. $ \frac{x}{y-x}$
• D. $ \frac{x}{y}$

Answer 1

Answer: (D)

If x number of waves of wavelength $\lambda_{1}$ and y number of waves of wavelength $\lambda_{2}$ are present in same distance s, then
$s=x \lambda_{1}=y \lambda_{2}$
or $\frac{x}{y}=\frac{\lambda_{2}}{\lambda_{1}}=\frac{n_{1}}{n_{2}} $
$\frac{n_{1}}{n_{2}}=\frac{x}{y}$