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?

The correct option is C because a mirage is primarily caused by terrestrial heating and the refraction of light.

Terrestrial heating occurs when the sun heats the ground, which in turn heats the layer of air directly above it. This creates a temperature gradient where the air near the ground is much hotter and less dense than the cooler air above it.

Refraction of light occurs as light rays from the sky pass through these layers of air with different densities. The light rays bend or refract progressively as they move from the cooler, denser air into the hotter, thinner air. Eventually, the light undergoes total internal reflection, which is a specific form of refraction at a critical angle, causing the light to curve back up toward the eye.

The observer perceives this bent light as a reflection on the ground, typically appearing as a pool of water or a shimmering surface. Since terrestrial heating creates the necessary conditions and refraction bends the light to create the illusion, 1 and 3 are the essential phenomena involved.