An optical fibre is made of glass fibre of refractive index 1.68. The outer coating of the glass fibre is made of material of refractive index1.44. What is the range of angles of the incident rays with the axis of the pipe for which total internal reflection inside the optical fibre takes place?

An optical fibre is made of glass fibre of refractive index 1.68. The

1.	An optical fibre is made of glass fibre of refractive index 1.68. The outer coating of the glass fibre is made of material of refractive index1.44. What is the range of angles of the incident rays with the axis of the pipe for which total internal reflection inside the optical fibre takes place?
Answer» Solution :We know the MAXIMUM launching angle in case of optical fibre as `i_(max)=sin^-1 (sqrt(mu_2^2-mu_1^2))` `=sin^-1 (sqrt((1.68)^2-(1.44)^2)=sin^-1(0.8653)=59^@ 55.` This is the maximum VALUE of i. Alllight rays with angle of incidence between `0^@ and 59^@.55.` will UNDERGO total internal reflection.