Please answer only experts Refractive index of a medium is 2.5. it means that, Speed of light in that medium is 2.5 times the speed of light in water. Speed of light in that medium is 2.5 times the speed of light in vacuum. Speed of light in that medium is (1/2.5) times the speed of light in vacuum. Speed of light in that medium is (1/2.5) times the speed of light in water. Share with your friends Share 0 Vipra Mishra answered this Dear Student μ = 2.5μ=cv=Speed of light in vacuumSpeed of light in medium2.5=Speed of light in vacuumSpeed of light in mediumSpeed of light in medium =12.5 Speed of light in vacuum Hence correct option is 3. Regards 1 View Full Answer