If $\mu_1$ and $\mu_2$ are the refractive indices of the materials of core and cladding of an optical fibre,then the loss of light due to its leakage can be minimised by having

An optical fiber works on the principle of ......

$A$ beam containing red,green,and blue light is incident on a prism. Their refractive indices are $1.39, 1.44$,and $1.47$ respectively. Then,the prism:

$A$ ray of light is incident at an angle $i$ from a denser to a rarer medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection is $r$ and the angle of refraction is $r'$. Then the critical angle $C$ will be:

Four rays $1, 2, 3$ and $4$ are incident normally on the face $PQ$ of an isosceles prism $PQR$ with apex angle $\angle Q = 120^{\circ}$. The refractive indices of the material of the prism for the above rays $1, 2, 3$ and $4$ are $1.85, 1.95, 2.05$ and $2.15$ respectively and the surrounding medium is air. Then,the rays emerging from the face $QR$ are

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