A light enters a transparent glass slab of refractive index $\mu=\large\frac{3}{2}$. The reflected ray and refracted ray are mutually perpendicular, The angle of incidence is

Question

$(a)\;\sin ^{-1} \bigg(\frac{3}{2}\bigg) \\ (b)\;\sin ^{-1} \bigg(\frac{2}{3}\bigg) \\ (c)\;\tan ^{-1} \bigg(\frac{3}{2}\bigg) \\ (d)\;\tan ^{-1} \bigg(\frac{2}{3}\bigg)$