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A star sometimes brighter and at other t...

A star sometimes brighter and at other times fainter. What is this effect called ? State the reason.

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This defect is called twinkling of stars. Reasons: The light from the stars will be passing through the atmosphere whose refractive index keeps changing constantly due to wind and varying air density. Thus, there will be changes in the density of light from the star reaching our eyes causing twinkling effect.
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ZEN PUBLICATION-THE HUMAN EYE AND THE COLOURFUL WORLD-ZEN ADDITIONAL QUESTIONS SECTION - SHORT ANSWER TYPE QUESTIONS - I
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  7. When a beam of white light is passed through a triangular glass prism,...

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  8. Name the phenomenon responsible for (i) advance of sunrise (ii) colour...

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  9. A star sometimes brighter and at other times fainter. What is this eff...

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  10. Why do we see a rainbow in the ske only after rainfall ?

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  11. Mention any four phenomena that can be observed due to atmospheric ref...

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  12. What is the difference in colours of the sun observed during sunrise/s...

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  13. Sun appears red in colour during sunrise but appears white at noon. Ex...

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  14. Why does the sun seem to rise two minutes before the actual sunrise an...

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  15. The sun near the horizon appears flattened at sunset and sunrise. Expl...

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  16. Is the position of a star as seen by us its true position ? Justify yo...

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  17. "Stars appear higher than they actually are". Give reason.

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  18. Explain how the colour of the scattered light depends on the size of t...

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  19. What would have been the colour of the sky, in the absence of atmosphe...

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  20. What is meant by scattering of light ? Use this phenomenon to explain ...

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