Optics III Magic of Atmospheric Refraction

Optics- III

Refraction of light talks about bending of light when light moves from one transparent medium to another , this small change creates wonderful change around.

Let's know:

Rainbow mind map of Refraction of light :-

Some natural phenomena

Mirage

                     

is an optical phenomenon which creates an illusion of the presence of water and is a result of refraction followed by Total internal reflection of light from a non-uniform medium ( different layers of air with different densities ).

Mirage is observed mainly during sunny days when driving on a roadway and in deserts on hot day.

Cause of Mirage:- 

 Refraction followed by Total Internal Reflection-  

Refraction:- Bending of light when moves from one medium to another medium  

Total internal Reflection:- when light moves from denser medium to rarer medium, when angle of incidence is more than critical angle Reflection takes place in place of refraction called Total internal Reflection

Explanation:- 

Mirages are most common in deserts. They happen when light passes through two layers of air with different temperatures. In desert, sun heats the sand, which in turn heats the air just above it,making it rarer medium, air above it denser medium, layer above is denser than lower and so on.The hot air bends light rays and refraction takes place between some layers of air.when angle of incidence becomes more than critical angle, in place of refraction,reflects takes place called Total internal reflection .

Early sunrise and delayed sunset - are the two phenomena that are caused again  due to the atmospheric Refraction of light 

Explanation: 

The Sun is visible to us two minutes before the sunrise and two minutes after the sunset because of the bending of the light due to atmospheric refraction. 

The density of air is higher near the surface of earth. The rays from the sun coming through space enter from rarer to the denser medium and hence bend slightly towards normal at each refraction and the human eye sees the sun rays as a straight line, which appears as the sun has risen which is its apparent position , but  actually not yet still below horizon actual position  becomes visible to us before actual sunrise.

 

The sun, after sunset, is setting below the horizon. Now, the apparent position of the sun is visible to us and not the actual position. This is again magic of atmospheric refraction.

Link for the post of Optics I (Properties of Light)

Link for the post of Optics II ( Reflection of light)

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                Abhilasha Jha