When a ray of light is incident at an angle $\theta=60^{\circ}$ on an air-glass interface, the reflected ray is 100 percent plane polarised. The value of the refractive index of the glass with respect to air $\left(a^{n} g\right)$ is given by:

1.732

The correct answer is Option (4) → 1.732

According to Brewster's law,

$μ=\tan θ_B$

$⇒μ=\tan (60°)$ [Brewster Angle, $θ_B=60°$]

$⇒μ=\sqrt{3}≃1.732$