A long optical fibre is gently bent into a circular arc of large radius.
(i) Explain qualitatively why bending the fibre can lead to loss of transmitted optical power.
(ii) Using the concept of the critical angle at the core–cladding boundary, describe with the help of a labelled sketch how bending changes the internal ray angles and thus affects total internal reflection.
(iii) State any two practical design measures adopted in communication fibres to reduce bending losses and briefly justify each measure.