The bouncing is more a metaphor, the refraction of light bending at an angle is sort of like how if you as an exterior observer look at a person who is standing waist deep in a very calm and clear swimming pool, their legs appear to be at a different position than their torso. Now imagine that 'bending' repeating trillions of times.

https://www.aflhyperscale.com/articles/how-do-fiber-optics-w...