Sunday, June 9, 2013


Condition for total internal reflection
1.Light travel from a denser to rarer medium
2.i > C in denser medium for a pair of media in contact

Suppose that a laser beam is submerged in a tank of water and pointed upwards towards water-air boundary.

The maximum possible angle of refraction is 90-degrees. If the angle of refraction were greater than 90 degrees, then the refracted ray would lie on the incident side of the medium. There is some specific value for the angle of incidence (the critical angle) that yields an angle of refraction of 90-degrees.Any angle of incidence that is greater than the critical angle would not result in refraction. All of the energy (the total energy) carried by the incident wave to the boundary stays within the water and undergoes reflection off the boundary. When this happens, total internal reflection occurs.

Application : Mirage
A traveler has lost his way in the desert. Enduring thirst and hunger, he suddenly saw an oasis, so the overjoyed man quickly ran towards it. To his great disappointment, it was just an illusion produced by a mirage. Its formation is a result of the refraction and the total internal reflection of light in the air. 

The Formation of Mirage
 In regions of air with temperature decreases with altitude, light will travel in a curved path due to refraction.
Refraction occurs when a light beam travels from glass to the air. The angle of incidence i is smaller than the angle of refraction r.
Total internal reflection occurs when the incident angle i is larger than the critical angle c.
The path of light when a mirage happens. 
Mirage is an optical illusion


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