When using fiber optics to transfer a signal, what must the light do?

The correct choice relates to the concept of total internal reflection, which is the principle that allows optical fibers to transmit light signals effectively. When light is introduced into a fiber optic cable, it must enter the "cone of acceptance." This is essentially the range of angles at which light can enter the fiber and still be guided along its core through total internal reflection.

If light enters the fiber at an angle greater than the cone of acceptance, it will not be adequately confined within the core and instead will be lost, resulting in signal degradation or loss. The cone of acceptance is determined by the refractive indices of the core and cladding materials of the fiber, which dictate the angles of incidence that will lead to efficient transmission of the signal through the fiber optics.

This concept highlights the importance of proper alignment and angle when connecting fiber optics, ensuring maximum light transmission and minimal signal loss. The other options, while pertinent to different aspects of fiber optics, do not directly address the requisite condition for effective signal transfer in terms of light entry into the fiber.