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| Numerical - 28 |
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| 28. In a star, hydrogen emits waves of l = 650 nm. The “red-shift” in the wave length is 1.5 nm. What is the speed of the star with respect to Earth? |
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| Suggested solution: |
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| Since a 'red-shift' is observed, the star is moving away from the Earth. |
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| Let v be the speed of the star. |
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| Obviously, |
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| Given : Dl = 15 A = 15 x 10-10m, l = 6.5 x 10-7, c = 3 x 108ms-1 |
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| = 6.923 x 105ms-1 |
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