Que 1st and 2nd with explanation.

1.  A ray incident at point B at an angle of  incidence $\theta$ enters into a glass sphere and is reflected and refracted at the farther surface of the sphere, as shown.  The angle between the reflected and refracted rays at this surface is 90$°$ .  If refractive index of material of sphere is $\sqrt{3},$ the value of $\theta$ is
$a) \mathrm{\pi }/3 \mathrm{b}) \mathrm{\pi }/4 \mathrm{c}) \mathrm{\pi }/6 \mathrm{d}) \mathrm{\pi }/12$

2.  Light in incident from glass $\left(\mu =1.5\right)$ to water $\left(\mu =\frac{4}{3}\right)$.  Find the range of deviation for which there are two angle of incidence.
$a) {\sin }^{-1}(8/9) to \mathrm{\pi }/2 \mathrm{b}) 0 \mathrm{to} {\sin }^{-1}(8/9) \mathrm{c}) 0 \mathrm{to} {\cos }^{-1}(8/9) \mathrm{d}) {\cos }^{-1}\left(8/9\right)\mathrm{to} \mathrm{\pi }/2$