Why does total internal reflection occur in a bicycle reflector?

since there is no light absorption.

This is a much more complex problem than just having "total reflection"—a simple mirror accomplishes that—but also having the light return to its original source in a way that allows the car driver, for example, to see the cyclist.

Total internal reflection occurs in a bicycle reflector because the reflector is designed with a coating of a material that has a higher refractive index than the surrounding air. When light enters the reflector at a certain angle (greater than the critical angle), it undergoes total internal reflection, bouncing off the reflective coating and remaining within the reflector instead of passing through it. This ensures that light entering the reflector from various angles, such as from the headlights of a car, is redirected back toward the source, increasing visibility for the cyclist.