# Frequence of light of galaxy receding from earth

• matt72lsu
In summary, most galaxies in the universe are moving away from Earth and a particular galaxy emits orange light with a frequency of 5e14 Hz. If the galaxy is receding from Earth with a speed of 3325 km/s, the frequency of the light when it reaches Earth would be slightly less than 5e14 Hz. This can be calculated using the equation f' = f (1 - v/c), where f' is the frequency of the light when it reaches Earth, f is the initial frequency of the light emitted by the galaxy, v is the speed at which the galaxy is receding from Earth, and c is the speed of light.
matt72lsu

## 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.

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

## 1. What is the frequency of light from a galaxy that is receding from Earth?

The frequency of light from a galaxy that is receding from Earth is known as the redshift. It is caused by the Doppler effect and is a measure of how much the light has been stretched as it travels through space. The higher the redshift, the faster the galaxy is moving away from us.

## 2. How is the frequency of light affected by a galaxy's distance from Earth?

The frequency of light from a galaxy is affected by its distance from Earth due to the expansion of the universe. As the distance between Earth and the galaxy increases, the light is stretched and the frequency decreases. This is known as cosmological redshift.

## 3. Can the frequency of light from a galaxy change over time?

Yes, the frequency of light from a galaxy can change over time due to various factors such as the movement of the galaxy, the expansion of the universe, and interactions with other objects in space. This change in frequency can be observed through redshift measurements.

## 4. How is the frequency of light related to a galaxy's velocity?

The frequency of light from a galaxy is directly related to its velocity. As the galaxy moves away from Earth, the light is stretched and the frequency decreases. This relationship is known as Hubble's law and is used to calculate the velocity of galaxies based on their redshift.

## 5. Are there any other factors that can affect the frequency of light from a receding galaxy?

In addition to redshift caused by the expansion of the universe, the frequency of light from a receding galaxy can also be affected by gravitational lensing, which is the bending of light due to the gravity of massive objects. This can cause the light to appear at a different frequency than what would be expected based on the galaxy's velocity alone.

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