InterviewSolution
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InterviewSolution
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With what speed should a galaxy move with respect to us to that the sodium line at `589.0 nm` is observed at `589.6 nm` ?A. 206 km `s^(-1)`B. 306 km `s^(-1)`C. 103 km `s^(-1)`D. 51 km `s^(-1)` |
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Answer» Correct Answer - B The relation between v, c and `lambda` are ,`v lambda=c` For small change in v and `lambda`, `(triangle v)/(v)=(-triangle lambda)/(lambda)` As `triangle lambda =589.6-589.0=+0.6 nm` Therefore, using doppler shift `(triangle v)/(v)=(-triangle lambda)/(lambda)=(-v_("radial"))/(c)` or `-v_("radial")~=+c((0.6)/(589.0))=+3.06xx10^(5)ms^(-1)` ` " " =306kms^(- 1)` Therefore, the galaxy is moving away from us. |
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