The doppler effect on light (red and blue shifts)

In summary, the Doppler effect affects the observer's perception of the energy and frequency of a photon. A photon observed by a standing observer will have a different energy and frequency compared to a moving observer in the same direction as the light source. This is due to the energy that can be extracted from a wave-particle system. It is important to note that the energy of a photon cannot exceed its own energy. Therefore, in a blue shift, the photons do have more energy compared to their original lower frequency. This concept also applies to other objects, such as a baseball, where the speed of impact relative to the observer affects the amount of energy transferred. However, for light, the Doppler effect plays a role in changing the energy and
  • #1
kashiark
210
0
what does the doppler effect mean for an individual photon? for instance in a blue shift do the photons actually have more energy if they were originally a lower frequency?
 
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  • #2
The doppler effect is only true for the observer and it's point of view. Let's say that a red light photon is observed by a standing observer. A different observer that is in relative motion from the first one in the direction of the light source will observe a slightly blueshifted light, a more energetical ray ( orange yellow green etc ) in accordance with it's speed relative to the "red light standing observer". If the second observer were to move along the direction of the light he would see a less energetical ray ( infrared microwave etc). It's not a complicated thing to understand, because it all comes down to the energy that can e extracted from a wave particle system.

A baseball flying towards you would transfer a certain amount of energy if it hits you. if you move towards it you will receive more energy if you move along it's direction you will receive less.

Let's say a highly energetic particle is moving towards the earth. From our point of view that particle has a fixed amount of energy and a fixed speed. The particle on the other hand would see a object of huge mass traveling close to the speed of light towards it. There is no point in finding out what energy our Earth would have if it was traveling at near light speed, because the particle would never be able to extract more energy than it itself has, out of the system. Photons are energy waves so they will change in accordance with the system of observation, their wavelength that is.
 
  • #3
kashiark said:
what does the doppler effect mean for an individual photon? for instance in a blue shift do the photons actually have more energy if they were originally a lower frequency?
The answer to your question is yes.
 
  • #4
thanks guys :biggrin:
 
  • #5
Lok said:
A baseball flying towards you would transfer a certain amount of energy if it hits you. if you move towards it you will receive more energy if you move along it's direction you will receive less.

I think that is misleading. The ball transfers more or less energy to you because its speed relative to you at impact is higher or lower. that is no true for light, it always hits you at c, but it has more or less energy because of the doppler shift.
 

1. What is the doppler effect on light?

The doppler effect on light is the change in the frequency of light waves emitted by a source due to the relative motion between the source and an observer. This change in frequency can result in either a red shift (increase in wavelength) or a blue shift (decrease in wavelength).

2. What causes the doppler effect on light?

The doppler effect on light is caused by the relative motion between a source of light and an observer. If the source is moving away from the observer, the wavelength of the light waves appears longer, resulting in a red shift. If the source is moving towards the observer, the wavelength appears shorter, causing a blue shift.

3. How is the doppler effect on light used in astronomy?

The doppler effect on light is used in astronomy to study the relative motion of celestial objects. By analyzing the red and blue shifts of light emitted from distant stars and galaxies, scientists can determine the direction and speed of their motion. This helps in understanding the structure and movement of the universe.

4. Can the doppler effect on light be observed in everyday life?

Yes, the doppler effect on light can be observed in everyday life. An example of this is the change in the pitch of a siren as an ambulance or police car approaches and then passes by. As the vehicle moves towards the observer, the sound waves are compressed, resulting in a higher frequency (pitch). As the vehicle moves away, the sound waves are stretched, resulting in a lower frequency.

5. How does the doppler effect on light impact our understanding of the universe?

The doppler effect on light has a significant impact on our understanding of the universe. It allows us to measure the speed and direction of objects in space, which helps in studying the formation and evolution of galaxies and the expansion of the universe. It also plays a crucial role in the discovery of exoplanets and the search for extraterrestrial life.

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