Optical fibres are extensively used for transmitting information over long distances.
(a) Define (i) critical angle and (ii) total internal reflection.
(b) Explain why the core of an optical fibre is made with a slightly higher refractive index than the cladding.
(c) Describe what happens to a light ray that enters the fibre core at an angle to the axis smaller than the critical angle at the core–cladding interface.