Question

A light beam is directed parallel to the axis of a hollow cylindrical tube. When the tube contains only air, the light takes 8.72 ns to travel the length of the tube, but when the tube is filled with a transparent jelly, the light takes 1.82 ns longer to travel its length. What is the refractive index of this jelly?

Answer 1

1.208

Step-by-step explanation:

L = Length of tube

c = Speed of light in air

v = Speed of light in jelly

Time taken by light in tube

`(L)/(c)=8.72`

Time taken when jelly is present

`(L)/(v)=8.72+1.82\\\Rightarrow (L)/(v)=10.54\ ns`

Dividing the above equations we get

`(v)/(c)=(8.72)/(10.54)\\\Rightarrow (c)/(v)=(10.54)/(8.72)\\\Rightarrow n=1.208`

The refractive index of the jelly is 1.208