. Assertion In optical fibre, the diameter of the core is kept small.

Reason This smaller diameter of the core ensures that the fibre shouls have incident angle more than the critical angle required for total internal reflection.


Best Answer


Solution : In a point-to-point communication link using electrical signal, we use a conducting wire or a cable and the signal current is guided through the

conductor cable wire. Light cannot pass through metal but can pass through a transparent glass, polymer or dielectric. Therefore, optical transmission line (called optical fibre) is made from any of these materials. The core dimension of optical fibres is so small (~10 mm) that the light entering will almost essentially be having incident angle more than the critical angle and will suffer total internal reflection at the core-cladding boundary. Such successive total reflections at opposite boundaries will confine the light to the core as shown in figure.

Hence, option (a) is true.


Talk to Our counsellor