Question

summarize how many methods can be used to determine the index of refraction (n) of an optical material

Answer 1

Method 1 - Snell's Law -  n_air × sin(θ₁) = n₂ × sin(θ₂) .

n_{2 =} n_air × sin(θ₁) / sin(θ₂) .

Hence if we know angle of incident & angle of reflection the we can find out the refractive index

Method 2 -  Goniometric method - A goniometer-spectrometer is used to measure transmission at angle, including the angles of minimum deviation of light and n is calculated from Snell's law

Method 3 - Ellipsometric method -

Method 4 - Spectrophotometric methods

Conclusion - Hence ultimately in each method we need to apply Snell's law to find the the index of refraction