An iso–scale glass prism stands with its (horizontal) base in water as shown in the figure. An incident ray of light, above and parallel to the liquid surface and perpendicular to the prism’s axis, is internally reflected at the glass–liquid interface and subsequently re–emerges into the air. Refractive index of glass is $µ_g$ and liquid is $µ_\ell$ , then which relation holds good

$\mu_{g}^2-\mu_{\ell}^2 \geq \cos ^2 \theta\left(\mu_{g}^2+1-2 \mu_{\ell}\right)$

Obtain $\mu_{g} \sin (\theta+\phi) \geq \mu_{\ell}$ where $\phi$ is the angle in the glass between the ray and the normal to the surfaces at the point where it enters the prism.