The refractive index of a medium can be calculated by the use of the angle of incidence and angle of refraction, or the speed of light in air and the speed of light in the medium
The speed of light in air is 3×10⁸m/s.
then n= (speed of light in a air)/(speed of light in the medium.)
1.4=(3ₓ10⁸)/(speed of light in the medium)
speed of light in the medium=3ₓ10⁸m/s÷1.4= 2.1×10⁸m/s
=2.1×10⁸m/s
