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  • The 6563 Å Hα line emitted by hydrogen in a star is found to be red- shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.

Q10.11  The 6563 Å Hα line emitted by hydrogen in a star is found to be red-shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.

Answers (1)

best_answer

Given,

wavelength  Hα line emitted by hydrogen:

\lambda=6563*10^{-10}m

star is  red-shifted by

 \lambda'-\lambda=15*10^{-10}m

let velocity of the star be v

Now,

as we know,

\lambda'-\lambda=\frac{v}{c}*\lambda

from here

\lambda'-\lambda\frac{1}{{c}*\lambda }={v}

v=\frac{3*10^8*15*10^{-10}}{6563*10^{-10}}=6.87*10^5m/s

Hence speed at which star is receding away is 6.87*10^5m/s

Posted by

Pankaj Sanodiya

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