n:  Refractive index

v:  Speed of light (m/s)

c:  Speed of light in vacuum (m/s) = 3x10⁸ m/s

n =

Light travels faster in air than in water, so refractive index more for water than that for air.

Snell’s Law:

n₁.sin θ₁ = n₂.sin θ₂