What Causes Blue and Red Shift in Light?

In summary, blue shift and redshift refer to changes in the frequency of light received compared to the frequency at which it was emitted. This can occur due to Doppler shift when the emitter and receiver are in motion relative to each other, or due to gravitational time dilation and the expansion of space.
  • #1
alchemist
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what exactly is the blue and red shift? what happens? why does this happens?
 
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  • #2
Originally posted by alchemist
what exactly is the blue and red shift? what happens? why does this happens?

In astronomy, blue shift is when the frequency of light received is higher than the frequency at which it was emitted (in the reference frame of the emitter). Redshift is when the frequency is lower.

This can be due to Doppler shift when the emitter and receiver are moving relative to each other, similarly to how an approaching object sounds higher in pitch and a receding object sounds lower. This is because the emitter is either catching up with or lagging behind each wavefront that it emits, making the waves closer together or farther apart.

In general relativity, shifting of light can also occur because of gravitational time dilation (gravity influencing the rate at which wavefronts are emitted), or from the expansion of space itself stretching light and redshifting it.
 
  • #3
Welcome to Physics Forums, alchemist! :smile:

Well said, Ambitwistor.
 

Related to What Causes Blue and Red Shift in Light?

1. What is blue shift and red shift?

Blue shift and red shift are terms used to describe the change in wavelength of light emitted by an object as it moves towards or away from an observer. Blue shift refers to a decrease in wavelength, resulting in a shift towards the blue end of the visible light spectrum, while red shift refers to an increase in wavelength, resulting in a shift towards the red end of the spectrum.

2. What causes blue shift and red shift?

Blue shift and red shift are caused by the Doppler effect, which is the perceived change in frequency or wavelength of a wave due to the relative motion between the source of the wave and the observer. This effect is commonly observed in sound waves, but also applies to electromagnetic waves such as light.

3. How are blue shift and red shift used in astronomy?

In astronomy, blue shift and red shift are used to determine the speed and direction of objects in space. By measuring the amount of shift in the wavelength of light emitted by celestial objects, scientists can calculate the velocity at which these objects are moving towards or away from Earth.

4. What is the significance of blue shift and red shift in the study of the universe?

The presence of blue shift and red shift in the light emitted by celestial objects is evidence of the expansion of the universe. Red shift is commonly observed in distant galaxies, indicating that they are moving away from Earth and that the universe is expanding. On the other hand, blue shift can be observed in objects that are moving towards Earth, such as stars in our own galaxy.

5. How is the concept of blue shift and red shift applied in everyday life?

Blue shift and red shift are not only relevant in the field of astronomy, but can also be applied in everyday life. For example, the Doppler effect is used in radar technology to measure the speed of moving objects, such as cars or aircraft. It is also used in medical imaging techniques, such as ultrasound, to measure the velocity of blood flow in the body.

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