The refractive index of water of kerosene , turpentine and water are 1.44 , 1.47,1.33 respectively . In which of these materials does light travel fastest and slowest?

Refractive Index = Velocity of light in air  

 Velocity of light in medium

So, if velocity of light in medium is faster, the refractive index would be lesser.

So fastest in water and slowest in turpentine.