Magical Mirages

Optical illusions often deceive our eyes during magic shows. On the other hand, on very hot days, you may notice a glistening watery image on the road in the distance that disappears as you approach it. This natural optical illusion, the mirage, is a trick that nature plays on our eyes.

Photo credit: EPOD

A mirage if an image of an object that is different from the form and location of the actual object. They often appear as a pool of water in the desert or a hot road but the water is not really there. The answer to this phenomenon is with how light interacts with the atmosphere.

Photo credit: University of Wisconsin

Normally, light travels in a straight line but it can bend and change direction depending on what it is passing through. This is a principle of refraction. A mirage occurs whenever light passes through layers of air at different temperatures. For instance, on a very hot day, the ground is warmer than the air above it. As light travels down from the cool air to the warmer air, it gets refracted upwards.

When this light reaches out eyes, our brain doesn’t see it as bent light. Instead, it thinks that the light has traveled in a straight line. Hence, it ‘thinks’ that some must have come from something on the ground and not in the sky. What you see then is a refracted image of the sky on the ground that resembles a pool of water. The most commonly know mirages are the inferior and superior images.

 Photo credit: University of British Columbia

 

In an inferior image, the inverted image is seen just below the object. It is the commonly seen during a hot day when air near the ground is warmer compared to the air above it. When sunlight passes through the layers (cooler to warmer), it produces images of the objects on the ground. The images gives an illusion of a ‘pool’.

 Photo credit: University of British Columbia

On the other hand, a superior image is one that appears above the original object. On icy surfaces or over large bodies of water, the lower layer of air is cooler than the one above it. This causes light to bend downwards from the object towards your eye. Hence, the mirage appears elevated of floating in the air.

So, the next time you see a mirage … Try to make a guess what type of mirage it is…

Resources

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s