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?

1. A mirage is an optical phenomenon caused by the bending (refraction) of light rays. 2. It typically occurs when the ground is very hot (Terrestrial heating - Statement 1), causing the air layers closest to the surface to be much hotter and less dense than the layers above. 3. As light from the sky travels downwards towards the hot ground, it passes through air layers of progressively lower density. 4. This change in density causes the light rays to bend upwards (Refraction of light - Statement 3). 5. An observer perceives this refracted light as coming from the ground, often creating an illusion of a pool of water (reflecting the sky) on the hot surface. 6. Reflection (Statement 2) and Diffraction (Statement 4) are not the primary mechanisms responsible for mirage formation. 7. Therefore, Terrestrial heating (1) creating the conditions and Refraction of light (3) being the optical process are the key phenomena involved.