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A distant star emits ultra-violet light of wavelength 121.6 nm. On Earth we observe this light...

A distant star emits ultra-violet light of wavelength 121.6 nm. On Earth we observe this light to have a wavelength of 122.5 nm. For the first answer, enter the letter T if the star is moving towards the Earth, or the letter A if moving away. For the second answer, give the magnitude of the relative velocity between the Earth and this star.

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Answer #1

Frequencies corresponding to the given wavelengths are

frequency emitted by star

frequency observed on Earth

As the observed frequency is less than the emitted fequency, the star is moving away from the Earth

Let Vstar be the speed of the star

then, by doppler effect, we have

where c is the speed of UV light

then,

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