Question

Question 4
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in the table.

$\begin{array}{cccc}Materialmedium& Refractiveindex& Materialmedium& Refractiveindex\\ Air& 1.0003& CanadaBalsam& 1.53\\ Ice& 1.31& -& -\\ Water& 1.33& Rocksalt& 1.54\\ Alcohol& 1.36& -& -\\ Kerosene& 1.44& Carbondisulphide& 1.63\\ Fusedquartz& 1.46& Denseflintglass& 1.65\\ Turpentineoil& 1.47& Ruby& 1.71\\ Benzene& 1.50& Sapphire& 1.77\\ Crownglass& 1.52& Diamond& 2.42\end{array}$

Answer 1

Using the information given in the table, the refractive index of kerosene is 1.44, that of turpentine is 1.47 and that of water is 1.33. Thus, water is having a lower refractive index and is optically rarer than kerosene and turpentine. The speed of light is inversely proportional to the refractive index. Therefore the light travels fastest in water because of its lower optical density.