Travellers on a hot road or in a desert sometimes see what looks like a pool of water in the distance, an illusion known as a mirage. What physical phenomenon causes a mirage?

Question

Mass numbers of two nuclei are in the ratio of 4:3. Their nuclear densities will be in the ratio of:

Answer 1

A mirage can also be understood by treating the layers of hot air near the ground as a natural, invisible curved mirror made purely of air.

Near the surface the air is thin and hot due to direct contact with the sun baked ground, and this hot layer bends light more sharply than the cooler air sitting above it.
As light from a distant part of the sky travels toward the observer, it keeps entering slightly less dense air the closer it gets to the ground, and this steadily bends the ray further away from the vertical.
Eventually the bending becomes so extreme that the ray cannot enter the hottest, thinnest layer at all, and it reflects internally, in much the same way light reflects inside an optical fibre or a glass prism during total internal reflection.
The reflected ray then travels back up to the observer's eyes, carrying the blue colour and brightness of the sky, so the ground appears to have a shiny, water like patch on it.
Because this whole effect depends entirely on how unevenly the air near the ground is heated, mirages are common on hot highways and in deserts, and they vanish once the ground cools or on overcast days.

Answer 2

A mirage can also be understood by treating the layers of hot air near the ground as a natural, invisible curved mirror made purely of air.

Near the surface the air is thin and hot due to direct contact with the sun baked ground, and this hot layer bends light more sharply than the cooler air sitting above it.
As light from a distant part of the sky travels toward the observer, it keeps entering slightly less dense air the closer it gets to the ground, and this steadily bends the ray further away from the vertical.
Eventually the bending becomes so extreme that the ray cannot enter the hottest, thinnest layer at all, and it reflects internally, in much the same way light reflects inside an optical fibre or a glass prism during total internal reflection.
The reflected ray then travels back up to the observer's eyes, carrying the blue colour and brightness of the sky, so the ground appears to have a shiny, water like patch on it.
Because this whole effect depends entirely on how unevenly the air near the ground is heated, mirages are common on hot highways and in deserts, and they vanish once the ground cools or on overcast days.

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