If Brewster's angle be 'θ', then the critical angle is

The correct answer is Option (1) → \( \sin^{-1}(\cot\theta) \)

Both angles are fixed by the refractive index \( \mu \) of the denser medium with respect to the rarer one. Brewster’s law gives the polarising angle, and the critical angle C is the angle of incidence in the denser medium for which the angle of refraction is \( 90^\circ \).

    \( \tan\theta = \mu \)

    \( \displaystyle \sin C = \frac{1}{\mu} = \frac{1}{\tan\theta} = \cot\theta \)

    \( C = \sin^{-1}(\cot\theta) \)