When the glass has a critical angle of 45°, what is the value of the refractive index?

Ans. If the glass has a critical angle of 45° and the refractive index is unknown, we use the formula that combines critical angle and refraction index. According to the formula,

μ = 1 / sin θ

μ = 1 / sin 45° = 1 / 0.5 = 2

Thus, the refractive index of the glass comes out to be 2.