The man can see an image of part of wall AB in the mirror. Point C is the point on the wall nearest to A that the man can see by reflection in the mirror. This point is not shown on Fig. 9.1. On Fig. 9.1, locate point C and draw a light ray from C that allows the man to see the image of C.
On the ray you have drawn in Fig. 9.1, mark the angle of incidence $i$ and the angle of reflection $r$.
Explain what the term virtual image means.
State one further characteristic of an image formed by a plane mirror.
Optical fibres guide light by total internal reflection. State two differences between total internal reflection and reflection in a mirror.
For light travelling from the material of the fibre to air, the critical angle is $44^{\circ}$. Calculate the refractive index of the material in the fibre.
Air is the medium from which light enters the optical fibre, and the angle of incidence is $50^{\circ}$. Calculate the angle of refraction.
Optical fibres are used in telecommunications to carry large amounts of data. Light pulses move through a fibre at almost the same speed as electrical pulses along a metal wire. State two advantages of using optical fibres rather than wires for transmitting data.