The phenomenon of mirage occurs due to which one of the following ?

A mirage is an optical phenomenon caused by the refraction and total internal reflection of light in the atmosphere. It occurs when there is a significant temperature gradient in the air, leading to a gradient in the refractive index [t1][t6]. In an inferior mirage, common over hot surfaces like deserts or roads, the air near the ground is much hotter and less dense than the air above it [t1][t7]. As light from a distant object or the sky travels downward toward the hot ground, it passes through layers of decreasing refractive index, causing the light rays to bend progressively away from the normal [t1][t5]. Eventually, the angle of incidence exceeds the critical angle, and the light undergoes total internal reflection, bending back upward toward the observer's eye [t7]. This creates a displaced or inverted image, often appearing as a pool of water reflecting the sky [t7].