Q. The optical fibres have an inner core of refractive index $n_{1}$ and a cladding of refractive index $n_{2}$ such that
A) $n_{1} = n_{2}$
B) $n_{1} \leq n_{2}$
C) $n_{1} < n_{2}$
D) $n_{1} > n_{2}$
Explanation
(d) Optical fibre is made of a thin glass core (diameter 10 to 100$\mu$m) surrounded by a glass coating called cladding is protected by a jacket of plastic.
The refractive index of the glass used for making core $\left( n_{1} = 1.7 \right)$ is a little more than the refractive index of the glass $\left( n_{2} = 1.5 \right)$ used for making the cladding $ie,\ n_{1} > n_{2}.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.