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

Explanation

The light travels fastest in that medium which has the lowest refractive index. Now, the refractive index of kerosene is 1.44, the index turpentine is 1.47 whereas the refractive index of water is 1.33. Here water has the lowest refractive index (of 1.33), so light travels fastest in water.