NCERT VI Social Sciences

Give reasons.

(a) The sun, the earth and the moon must be in a straight line for an eclipse to occur.
(b) The penumbra is faint.
(c) An aeroplane or a bird does not cast a shadow upon the earth.
(d) We get an upside down image in a pinhole camera.

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Answers

2015-04-05T20:09:33+05:30
A) If the sun, moon and earth are not in the same line a total eclipse cannot occur.
b) It is like being in the football stadium with light sources from 2 sides. You have 2 shadows. Individually, each of them can be considered as penumbra, and where they overlap - that's umbra.
c) When a bird or an aeroplane fly close to the ground shadows are actually formed, but when they go too high the clouds block the light. Therefore, no shadows of birds and aeroplanes are cast on the earth if they fly too high in the sky.
d) The aperture ( hole ) is so small it bends the light in a manner that shows an inverted image. It is not only inverted but also reverse.

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