Answer:
n = 1.4266
Step-by-step explanation:
Given that:
refractive index of crystalline slab n = 1.665
let refractive index of fluid is n.
angle of incidence θ₁ = 37.0°
Critical angle


According to Snell's law of refraction:

At point P ;


Therefore:

Then maximum value of refractive index n of the fluid is:


n = 1.4266