Correct Option
A mirage is an optical phenomenon primarily caused by terrestrial heating and the refraction of light. On hot surfaces, such as roads or deserts, the ground intensely heats the air directly above it. This creates a temperature gradient, resulting in layers of air with varying densities and, consequently, different refractive indices. Cooler, denser air is found higher up, while warmer, less dense air is closer to the surface. As light rays from distant objects travel from the cooler, denser air towards the warmer, rarer air near the ground, they continuously bend upwards, away from the normal, due to refraction. This curved path of light causes an observer to perceive the object as being in a different, often inverted, position, creating the illusion of a reflective surface like water.
Incorrect Options
Reflection of light is not the primary mechanism behind mirage formation. While light is involved, the phenomenon relies on the bending of light rays (refraction) as they pass through air layers of varying densities, rather than light bouncing off a surface.
Diffraction of light, which describes the bending of light waves as they pass around obstacles or through an aperture, is not a contributing factor to the formation of mirages. Mirages are a result of the gradual bending of light through a medium with a continuously changing refractive index.