what is mirage explain the condition under which it is seen
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Mirage is an optical illusion and it occurs due to total internal reflection.On hot summer days,air near ground becomes hotter than the air at higher levels.Refractive index of air increases with increase in density.Hotter air is less dense and has less value of refractive index than cooler air.If air is still,the optical density at different levels of air increases with height.
As a result,light from a tall object passes through a medium whose refractive index decreases towards the ground.
thus a ray of light from such an object bends away from normal and undergoes total internal
reflection.Thus,if the angle of incidence is more than the critical angle,TIR takes place.
To a distant observer,light appears to come from a point below the ground (and it seems to the observer that if some water is present there ).
Hence the conditions for TIR are
1.The light must travel from optically denser medium to optically rarer medium.
2.The angle of incidence must be greater than the critical angle.
As a result,light from a tall object passes through a medium whose refractive index decreases towards the ground.
thus a ray of light from such an object bends away from normal and undergoes total internal
reflection.Thus,if the angle of incidence is more than the critical angle,TIR takes place.
To a distant observer,light appears to come from a point below the ground (and it seems to the observer that if some water is present there ).
Hence the conditions for TIR are
1.The light must travel from optically denser medium to optically rarer medium.
2.The angle of incidence must be greater than the critical angle.
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