A star is moving away from the Earth. An obse | vedclass

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(B) According to the Doppler effect for light,when a source (star) moves away from an observer (Earth) with a velocity $v$,the observed frequency $
u

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(B) According to the Doppler effect for light,when a source (star) moves away from an observer (Earth) with a velocity $v$,the observed frequency $
u^{\prime}$ is given by:$
u^{\prime} = 
u \left( \frac{c}{c+v} ight)$where $
u$ is the actual frequency,$c$ is the speed of light,and $v$ is the velocity of the star.Since the star is moving away,the denominator $(c+v)$ is greater than $c$,which implies $
u^{\prime} We know the relationship between frequency and wavelength is $
u = \frac{c}{\lambda}$,which means $\lambda = \frac{c}{
u}$.Since the observed frequency $
u^{\prime}$ decreases,the observed wavelength $\lambda^{\prime} = \frac{c}{
u^{\prime}}$ must increase. This phenomenon is known as a redshift.

$A$ star is moving away from the Earth. An observer on the Earth will see the wavelength of light coming from the star as:

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