Frequence of light of galaxy receding from earth

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SUMMARY

The discussion centers on calculating the frequency of light emitted from a receding galaxy, specifically one emitting orange light at a frequency of 5e14 Hz and receding at a speed of 3325 km/s. The correct formula to use is f' = f (1 - v/c), where v is the speed of the galaxy and c is the speed of light. The user initially miscalculated the frequency upon reaching Earth, mistakenly converting Hz to fHz, which led to confusion. The expected outcome is that the observed frequency will be slightly less than 5e14 Hz due to the Doppler effect.

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  • Understanding of the Doppler effect in light
  • Familiarity with the speed of light (c = 3e8 m/s)
  • Basic algebra for manipulating equations
  • Knowledge of frequency units (Hz)
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Homework Statement



Most of the galaxies in the universe are observed to be moving away from Earth. Suppose a particular galaxy emits orange light with a frequency of 5e14 Hz.

1) If the galaxy is receding from Earth with a speed of 3325 km/s, what is the frequency of the light when it reaches Earth?

Homework Equations



f ' = f ( 1 - v/c)

The Attempt at a Solution


I did:

f ' = 5e14 (1- 3.325e6/3e8) then converted Hz to fHz and got 4.9e29 but it was wrong.
 
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finger+calculator error

You need to have an estimate of the answer to know if you hit the wrong buttons.
3300km/s is tiny compared to light speed, so 1-v/c is going to be only slightly less than 1, so your answer is going to be slightly less than 5E14.

"then converted Hz to fHz"
what does this mean? whatever it means it was wrong
 


i reworked it and no clue what I am doing wrong. and the answer says it's in fHz
 

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