Question

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

Answer 1

Speed of light in a medium is given by the relation for refractive index (n_m). The relation is given as 
\(n_m = \frac{\text{Speed of light in air }}{\text{Speed of light in the medium}} =\frac{ c }{v}\)

\(⇒v=\frac{c}{n_m}\)

\(⇒ v∝\frac{1}{n_m}\)
It can be inferred from the relation that light will travel the slowest in the material which has the highest refractive index and travel the fastest in the material which has the lowest refractive index. 
It can be observed from table that the refractive indices of kerosene, turpentine, and water are 1.44, 1.47, and 1.33 respectively. Therefore, light travels the fastest in water.