What is the driving factor behind total internal reflection occurring?

Total internal reflection occurs when a wave traveling in a denser medium strikes the boundary of a less dense medium at a certain angle, known as the critical angle. The incident angle of the wave is crucial because if it exceeds this critical angle, the wave cannot pass into the less dense medium and is instead completely reflected back into the denser medium. This phenomenon is fundamentally linked to the wave properties at the interface of two different media, where the speed and direction of light change.

In contrast, while the frequency of the wave, the medium’s density, and the temperature can all influence wave behavior in various ways, they do not directly cause total internal reflection. For instance, frequency affects wave speed and wavelength in different mediums, but it does not determine the occurrence of total internal reflection directly. Similarly, the medium's density is a factor in determining what the critical angle will be, but it is the incident angle of the wave that ultimately determines whether total internal reflection occurs. Temperature can impact the density and speed of sound or light waves in a medium, but it doesn't have a direct influence on whether total internal reflection takes place.