Why mirage formation is applicable only for distant objects?
Dear Student,
Mirage formation is more evident when the more refraction takes place from the layers of air at different temperatures which will occur in case of low glancing angle. During heated summer, the ground is hot and air is cool. So the layers of air close to the ground shows a greater temperature gradient. At low glancing angle more light will pass through such heated layers and thus suffers more refraction and is more likely to approach an angle greater than the critical angle and suffer a total internal reflection and the light is finally reflected upwards. So, an inverted image of the object finally appears in the same way as in case of reflection from a water surface. For nearer objects, path of light travelled is less and hence it encounters less number of layers with different refractive indices and doesn't suffer a total internal reflection which can lead to mirage.
Regards
Mirage formation is more evident when the more refraction takes place from the layers of air at different temperatures which will occur in case of low glancing angle. During heated summer, the ground is hot and air is cool. So the layers of air close to the ground shows a greater temperature gradient. At low glancing angle more light will pass through such heated layers and thus suffers more refraction and is more likely to approach an angle greater than the critical angle and suffer a total internal reflection and the light is finally reflected upwards. So, an inverted image of the object finally appears in the same way as in case of reflection from a water surface. For nearer objects, path of light travelled is less and hence it encounters less number of layers with different refractive indices and doesn't suffer a total internal reflection which can lead to mirage.
Regards