The correct answer for the given question is option 4, which states that a mirage is an illustration of both refraction and total internal reflection of light.

To understand why option 4 is the correct answer, we need to break down the concept of a mirage. A mirage is an optical phenomenon where there is a distortion or illusion of objects in the distance, often observed in deserts or on hot roads. It occurs due to the bending of light as it passes through different layers of air with varying densities.

Refraction is the bending of light when it passes from one medium to another of different optical density. In the case of a mirage, the hot air near the ground has a lower density than the cooler air above it. This difference in densities causes the light to bend as it passes from the cooler air to the hotter air, creating a mirage.

Total internal reflection occurs when light is completely reflected back into a medium instead of being refracted out of it. In the case of a mirage, a layer of hot air near the ground acts as a medium with a lower refractive index than the cooler air above it. This causes the light to undergo total internal reflection at the boundary between the two layers, creating the illusion of a reflected image.