Question

Q8. 'The refractive index of water is 4/3' This means:
a.
The speed of light in air is 3/4 times faster than speed of light in water.
b.
The speed of light in water is 3/4th the speed of light in vacuum.
The speed of light in air is 1/4 times the speed of light in water.
d.
None of the given options
Marks: 1​

Answer 1

Given :

Refractive index of water = 4/3

To Find :

We have to find relation between speed of light in vacuum and speed of light in water$.$

Concept :

Refractive index of a medium is defined as the factor by which speed of light reduces as compared to the speed of light in vacuum.

$\bigstar\:\underline{\boxed{\bf{\gray{n=\dfrac{c}{v}=\dfrac{speed\:of\:light\:in\:vacuum}{speed\:of\:light\:in\:medium}}}}}$

Calculation :

$\dashrightarrow\rm\:\dfrac{4}{3}=\dfrac{speed\:of\:light\:in\:vacuum}{speed\:of\:light\:in\:water}$

$\dashrightarrow\underline{\boxed{\rm{\blue{speed\:of\:light\:in\:water}=\green{\dfrac{3}{4}}\times\purple{speed\:of\:light\:in\:vacuum}}}}\:\orange{\bigstar}$

Option-B is the correct answer.