Question

You are given water, mustard oil, glycerin and kerosene. In which of these media a ray of light incident obliquely at the same angle would bent most?
A. Kerosene
B. Water
C. Mustard oil
D. Glycerin

Answer 1

To solve this question, we need to compare the refractive indices of the given materials. We must know that the refractive index of a material is given as the ratio velocity of light through vacuum to the velocity of light through the given medium. The bending of light will be more in the medium which has a more refractive index.

Complete step by step answer:
We should have an idea about refractive index before solving the question. Refractive index of a material is the measure of how light propagates through a material. That means higher the refractive index, the slower the light travels, which causes a correspondingly increased change in the direction of light within the material. Therefore, higher the refractive index of the material, the incident ray will bend more.
Now, the refractive index of a material is given by ratio of velocity of light in vacuum to the velocity of light in the given medium. That is
$n=\dfrac{c}{v}$
Where, $c$ is the velocity of light in vacuum given as $3\times {{10}^{8}}$.
$v$ is the velocity in the given medium.
We have the refractive index of water, mustard oil, glycerin and kerosene as,
$\begin{aligned} & {{n}_{\text{water}}}=1.33 \\\ & {{n}_{\text{mustard oil}}}=1.47 \\\ & {{n}_{\text{glycerin}}}=1.473 \\\ & {{n}_{\text{kerosine}}}=1.44 \\\ \end{aligned}$
So, the refractive index of glycerin is highest. Therefore, the ray bends the most in case of glycerin.

So, the correct answer is “Option D”.

Note:
We know that the bending of light depends upon the refractive index of the material. But, this bending of light follows the trend that if light ray is entering a denser medium from a rarer medium, it bends more towards the normal and if it is entering a rarer medium from a denser medium, it will bend away from the normal. The amount of bending depends on the change in speed of the light ray in the given medium and angle of incident ray.