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What are Mirages?


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The Physics of Mirages
Physics 211X  Fall 2010
John Dutton

    Light can be reflected and refracted. To understand a mirage you must first understand how temperature affects the path light takes. If light travels through constant temperature then it will travel in a straight line. Considering light as a photon it makes sense that these photons would take the shortest path. Much like electricity takes the path of least resistance. Cold air has a higher index of refraction than hot air does. This is due to the fact that cold air is more dense than hot air and light travels slower through it. 

    Air does not have uniform temperature. In fact it has layers of different temperatures that get lower as you climb in height. The picture above illustrates the path that light takes during an average mirage. In the case of a mirage you notice that the angle of refraction is greater than the angle of incidence. This bending of light makes you see the sky where there should be sand. Providing the illusion of water.

    Snell's Law is also known as the law of refraction. This equation illustrates the relationship between the angle of incidence and angle of refraction in relation to velocity (v) and index of refraction (n).

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