physics

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The yellow line emitted by a helium discharge tube in the laboratory has a wavelength of 587 nm
The same yellow line in the helium spectrum of a star has a measured
wavelength of 590 nm.

Calculate the speed of the moving star.

• physics -

Doppler effect
Frequency (observed) f=c/λ=3•10⁸/5.87•10⁻⁷=5.11•10¹⁴ Hz
Frequency (apparent) f´=c/λ´=3•10⁸/5.9•10⁻⁷=5.085•10¹⁴ Hz
f'=cf/(c+u)

u=c{(f/f´)-1} =1.53•10⁶ m/s

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