Answer Posted / sanju

In cold regions, the air touching the surface of the earth
is extremely cold and hence it is denser than the air which
is higher than the surface. When a ray from a boat travels
more and more away from the normal. Finally, the angle of
incidence becomes grater than the critical angle and total
internal reflection takes place. Now, on traveling downwards
the rays pass from rarer into denser layers and are bent
more and more towards the normal. At last they enter the eye
of the observer. To him it appears to come from some other
point. Similarly, the image of every point of the boat is
formed high up in the air and whole of the boat appears
hanging upside down in the air.

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