Medical use of optical fibres
Optical fibres are often used in medical procedures. One example is to use an endoscope to illuminate and visualise areas that we couldn't normally see. We used to have to operate to see what the problem was.
If you were to see the end of the endoscope this is what you would see.
Two of the main fibre optic features used in an endoscope are cables that light up (illuminate) the inside of the stomach. The other main feature is a fibre optic cable that allows you to see what the problem is:
Both of these fibre optic cables rely on total internal reflection. Without this neither feature would work.