Question -
Answer -
(a) Refractiveindex of the glass fibre, 
Refractive index of the outer covering of thepipe, 
= 1.44 Angle of incidence = i
Angle of refraction = r
Angle of incidence at the interface = i’
The refractive index (μ) of the innercore − outer core interface is given as:
For the critical angle, total internalreflection (TIR) takes place only when
, i.e., i > 59°
Maximumangle of reflection,
Let,
be the maximum angle ofincidence.
Therefractive index at the air − glass interface,We have the relation forthe maximum angles of incidence and reflection as:
Thus, all the rays incident at angles lyingin the range 0 < i < 60° will suffer total internalreflection.
(b) If the outer covering ofthe pipe is not present, then:
Refractiveindex of the outer pipe,
For the angle of incidence i =90°, we can write Snell’s law at the air − pipe interface as:
