CBSE Class 10 Answered

Inferior mirage, it is called so because the inverted image lies below the erect one.

In the desert, the air is very hot. The air near the surface of the earth is hot and is less dense. As you go up and away from the earth’s surface, the air becomes cooler and hence denser. Thus there are layers of air with higher density in the vertically upward direction. Rays of light from a shady oasis area bend away from the normal as they pass from the denser layer to the rarer layer. The angle of incidence increases for each successive layer. At a certain point, the rays of light will undergo total internal reflection. When the light reaches the eyes of a weary desert traveler, to him, the light will appear to emerge in a straight line in the backward direction, thus giving an impression of a water pool.  

Superior Mirage : The superior mirage forms when cold air lies beneath relatively warmer air(like over oceans). In this condition, light rays refract, or bend, toward the colder (and denser) air -- that is, downward. This bending causes the image of the object to appear to us to be above its actual position because our brains assume the light rays have taken a straight path from the object to our eyes.

The most common form of superior mirage is looming.

When an image appears much higher in the sky than the actual object's position, the condition is termed looming.

This is sometimes called the mirage of the desert, but today it is more appropriately known as the “hot-road” mirage, as it is seen on asphalt paving nearly every sunny day.