For a ray of light,the critical angle is minimum,when it travels from

Consider a glass cube slab of dielectric bound by the planes $x=0, x=a$; $y=0, y=b$; $z=0, z=c$; with $b > a > c$. The slab is placed in air and has a refractive index of $n$. The minimum value for $n$,such that all rays entering the dielectric at $y=0$ reach $y=b$ is

Write the definition of critical angle.

$A$ ray of light travels from a medium of refractive index $2$ to another medium of refractive index $\sqrt{2}$. Total internal reflection takes place when the angle of incidence is

$A$ ray of light incident parallel to the base $PQ$ of an isosceles right-angled triangular prism $PQR$ suffers two successive total internal reflections at the faces $PQ$ and $QR$ before emerging reversed in direction as shown below. If the refractive index of the material of the prism is $\mu$,then

If the critical angle for a material to air is $30^o$,the refractive index of the material will be