अक्टूबर 18, 2018

Why do stars twinkle in the night Sky ?
DWQA Questionsवर्ग: QuestionsWhy do stars twinkle in the night Sky ?
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ArifArif answered 4 महीना ago

Why do stars twinkle at night?
Stars are too far away in the sky to have a dimension. For all practical purposes, they can be modelled as point sources of light. At the same time, the Earth has an atmosphere. The Earth’s atmosphere is driven by a number of factors including heat from the Sun and Earth.
The irregular movement of wind is responsible for mixing smoke and water vapour to the various layers of the atmosphere. This instability also causes the density of the air to fluctuate locally. While it is not true for all media, the material density of air affects the refractive index of the air at the point.
If the density increases, the refractive index goes up. Hence, when light from a distant star enters the atmosphere, it does not suffer a straight path through the atmosphere. Instead, it travels in a zig-zag path. This is because Snell’s law dictates that the path taken by a refracted ray depends on the refractive indices of the media. The path can be easily changed when turbulence disturbs the refractive index of air in its path. Because it is a point source of light, the apparent position of the star keeps changing. This is what twinkling is.
You may notice that this does not happen to brighter objects in the sky like planets and the Moon. This is because they are extended sources of light. This means that they are composed of smaller, point sources. When these point sources shift due to turbulence, they do not affect the overall shape of the extended source. This means that the planets are more or less fixed while the stars twinkle.

Competition Mantraadmin asked 5 महीना ago

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