By using the Snell's law n i sin ⁡ ⁡ θ θ i = n t sin ⁡ ⁡ θ θ t where n i , n t , and θ θ i are the refractive index of the medium where the incident wave and the reflected wave exist, the refractive index of the medium where the transmitted wave exists, and the angle of incidence respectively,