Question

2. why do areoplane and bird flying in the sky not cast a shadow on the ground why
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Answer 1

Answer:

In this case the bird is opaque body and the Earth's surface is a screen. When the bird is flying high in the sky the distance between the body and the surface of the Earth is too large and hence even though the light is obstructed by the bird's body it cannot cast its shadow due to the large distance.

Answer 2

Answer:

Birds fly high in sky do cast their shadow but because they are shading an area that is very tiny,the shadow is not available,For the shadow to fall near you,the bird or plane would have to close to the line directly from you to the sun