The phenomenon of "Mirage", that is usually observed in deserts, is the result of which of the following?

Refraction of light

The correct answer is Option (2) → Refraction of light

The phenomenon of a mirage, commonly seen in deserts, occurs due to refraction of light caused by layers of air at different temperatures (and hence different densities). 

Note: Total Internal Reflection (TIR) plays a critical role in the formation of a mirage; however, it is important to understand that TIR is actually a specific consequence of continuous refraction. A mirage occurs because light rays bend (refract) successively as they pass through layers of air with varying temperatures and densities near the hot ground. This gradual refraction continues until the angle of incidence exceeds the critical angle, at which point Total Internal Reflection occurs to send the light upward to the observer's eye. Therefore, while TIR is the final stage of the process, the entire phenomenon is fundamentally rooted in the atmospheric refraction of light.