Mirage: An Optical Illusion

Suppose you are in the desert and you are lost in the desert. You have been walking for many hours. You have run out of water and you're thirsty. On the horizon, you see a big, shimmering puddle of water. "Yippeeeeeee", you shout. And thanks to God that you are saved! But when you approach at that place you found nothing.

Because...it's not a puddle of water. It's a mirage.

What is Mirage?

A mirage is an optical phenomenon that creates the illusion of a distant object or objects caused by the bending of light rays via refraction in layers of air of varying density. The word Mirage comes from the Latin mirari, meaning "to look at, to wonder at".

Normally, light waves from the sun travel straight through the atmosphere to our eyes. But, the light passes through different temperatures (hot air and cold air) at different speeds.

Mirages happen when the ground is very hot and the air is cool. The hot ground warms a layer of air just above the ground. When the light moves through the cold air and into the layer of hot air it is refracted. A layer of very warm air near the ground refracts the light from the sky nearly into a U-shaped bend but our brain thinks the light has travelled in a straight line.

In the above picture it looks like that there are mountains which are reflected in a lake but there might not be mountains at all.

Mirages are most common in deserts. Mirages happen when the Sun heats the sand of the desert, which in turn heats the air just above it. The hot air bends light rays and reflects the sky. When we see it from a distance, the different air masses colliding with each other act like a mirror. The desert ahead seems to have become a puddle of water but it is actually a reflection of the sky above.

Types of Mirage

Mirages are categorized into two kinds:

• Superior Mirage

In Superior mirage, the mirage image appears above the real object. It occurs when the air below is colder than the air above. This kind of unusual order, called temperature inversion.

Fata Morgana is an example of superior mirage which appears in the Straits of Messina, between Sicily and Italy. It is an image of a town in the sky, like a fairy tale landscape.

• Inferior Mirage

Interior mirage is one in which the mirage image appears below the real object. The images of inferior mirage are not stable.

Example of inferior mirage is a mirage which usually appears in the desert in southern Xinjiang from May to October, especially when the temperature is high.

Mirage is a real optical phenomenon which can be captured on camera, since the light waves or rays are actually bend via refraction to form the false image. Mirages can be seen almost anywhere. Those shimmering heat hazes that appear on the road ahead on sunny days, but disappear as we approach.

The End Notes

That's all in this article. I hope you liked it. Please comment your views and suggestions.

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