Final answer:
Light propagation through fibre optic cables is primarily described by c) total internal reflection, a key principle that enables efficient transmission of signals in communications.
Step-by-step explanation:
The propagation of light through a fibre optic cable is best described using the principle of c) total internal reflection. This principle applies to the transmission of light down fibres of plastic or glass, which are materials commonly used in fibre optics. The light is guided along the fibre as it repeatedly hits the inside surface of the fibre at an angle greater than the critical angle, resulting in it being totally internally reflected. This process allows for the light to be directed around corners, enabling the transmission of telephone, internet, and cable TV signals over long distances without significant loss of signal quality.