Question

What is total internal reflection and critical angle? What is the working principle of Optical Fibre. 
 

Hint:

Total internal reflection occurs when light moves from a denser to a rarer medium and strikes the boundary at an angle larger than the critical angle.

Answer 1

\textit{Total Internal Reflection:} Total internal reflection occurs when a light ray traveling from a denser medium to a rarer medium hits the boundary at an angle greater than the critical angle and reflects completely back into the denser medium. \textit{Critical Angle:} The critical angle \( \theta_c \) is the angle of incidence beyond which total internal reflection occurs. It is given by: \[ \sin \theta_c = \frac{n_2}{n_1}, \] where \( n_1 \) and \( n_2 \) are the refractive indices of the denser and rarer media, respectively. \textit{Working Principle of Optical Fibre:} An optical fibre works based on the principle of total internal reflection. Light signals are transmitted through the fibre by multiple total internal reflections within the fibre, which is made of a core with a higher refractive index than the cladding surrounding it.