The reasons for the occurrence of mirage phenomenon
The mirage can occur on the seas or in the deserts , it is a natural phenomenon that takes place on the desert at noon especially in the summer times , where the objects on the road sides seem as if they had inverted images on a wet area .
When the air above the desert road is heated at noon which leads to the formation of different air layers of different temperature by convection currents , and the mirage occurs when the ground heats the air above making it hotter than the air at higher altitudes .
When cold air is denser than warm air , and it has a greater refractive index , when the light travels at a shallow angle along a boundary between the air of different temperature , the light rays bend towards the colder air.
If the air near the ground is warmer than that higher up , the light ray bends upward , it will totally reflected above the ground , and the light rays curve downward , and the result is seeing the upright image and the inverted image which appears to you as a reflection in the water .
Types of mirage
The mirage is called also an inferior mirage which appears in the desert , it appear to be a lake of water in the distance , it is called inferior as the mirage is located under the real object , So , the inferior mirage causes the observer to see a bright and bluish patch on the ground in the distance .
The inferior mirage is usually upside down , it is not stable , when an object ( as a tree ) exists on the road side , the rays coming from it refract several times , going from the higher cold layers to the lower hot layers , and the hot-road mirage ( fake water ) on the road is the most common example of an inferior mirage .
At the hottest air layer ( which lies above the Earth surface directly ) , a total internal reflection happens to the rays coming from the object , So , this layer appears as a watery area and a virtual inverted image is formed below the object .
The heat haze is called the heat shimmer which refers to the inferior mirage that experienced when viewing the objects through a layer of heated air such as viewing the objects across hot asphalt or through the exhaust gases produced by jet engines , and it is called a highway mirage , and the the image is usually upside down .
The superior mirage occurs when the air below the line of sight is colder than the air above it , and it is less common than the inferior mirages , it is common in the polar regions over large sheets of ice that have a uniform low temperature .
The superior mirages also occur at more moderate altitudes , and they are weaker and tend to be less smooth and stable , and it can be right-side up or upside down depending on the distance of the true object and the temperature gradient .
The fata Morgana mirages are most common in the polar regions especially over large sheets of ice with a uniform low temperature , and it can be be observed on cold days , in desert areas , over oceans and lakes .
Fata Morgana appears with the alternations of compressed and stretched zones , the erect images , the inverted images , and it is also a fast-changing mirage .