A monochromatic light is incident from air on a refracting surface of a prism of angle 75° and refractive index n₀ = √3. The other refracting surface of the prism is coated by a thin film of material of refractive index n as shown in figure. The light suffers total internal reflection at the coated prism surface for an incidence angle of θ ≤ 60°. The value of n² is _____.