Consider the following natural phenomena : 1. Terrestrial heating 2. Reflection of light 3. Refraction of light 4. Diffraction of light Due to which of these phenomena is mirage formed ?

Mirages arise when terrestrial heating produces strong temperature gradients near the ground, causing layers of air with different densities and thus different refractive indices. Light rays travelling through these vertically varying layers are continuously bent (refracted), producing displaced or inverted images (inferior or superior mirages) rather than true mirror reflections. This mechanism—the bending of light by varying air refractive index due to temperature contrasts—is explicitly described as the cause of mirages [2]. Reflection or diffraction are not the primary causes; the effect is atmospheric (terrestrial) refraction produced by heating and resulting air-density gradients.

Sources

1. [1] https://ntrs.nasa.gov/api/citations/20250005322/downloads/Paper.pdf
2. [2] https://en.wikipedia.org/wiki/Atmospheric_refraction