Final answer:
To achieve total internal reflection, light must transition from a higher to a lower refractive index medium at an incident angle greater than the critical angle, a condition applied in fiber optics and endoscopic technology.
Step-by-step explanation:
Total internal reflection, complete reflection of a ray of light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle. If we want to create total internal reflection, the light must pass from a medium with a higher refractive index to a medium with a lower refractive index, and the incident angle must be greater than the critical angle.
The critical angle is the incident angle that produces an angle of refraction of 90°, and beyond this angle, all the light is reflected back into the medium. In applications such as fiber optics, light is transmitted down fibers of plastic or glass, utilizing the principle of total internal reflection. The fibers are coated with cladding, which prevents light from being transmitted between fibers in a bundle, ensuring efficient internal reflection. This principle is also employed in endoscopes, used for exploring the human body.