# Is the Doppler effect for atomic spectra a purely realistic effect?

• wdlang
In summary, the Doppler effect in a thermal atomic gas involves the emission of a photon by an atom traveling at a certain velocity. The momentum of the emitted photon can be determined using the free one approximation, and the energy of the photon can be calculated using the energy conservation law. While the Doppler effect may seem to depend on the mass of the atom, the formula given in the book only depends on the velocity of the atom. An example of calculating the Doppler shift is provided, showing that the wavelength of the photon does have a slight dependence on the mass of the atom, but the effect is minimal.
wdlang
i am now studying the Doppler effect in a thermal atomic gas

If an atom travels in velocity v along x direction

at some time, it emits a photon in some direction

the momentum of the emitted photon can be well approximated with the free one

thus the momentum of the atom after the emission is well defined

We can then determine the energy of the photon with the energy conservation law

In this procedure, the Doppler effect apprarently depends on the MASS of the atom

However, the fomulae given in the book does not depends on the MASS but only on the velocity of the atom

You might want to show an example where you calculate the Doppler shift according to your method. For example, let's say that a hydrogen atom is initially moving in the positive x direction at 0.1c, and it then makes a transition from an n=2 state to the ground state, emitting a photon in the positive x direction. What wavelength do you get for the photon (1) by your method, and (2) by the method given in your textbook?

It's true that the wavelength of the photon will depend, very slighly, on the mass of the atom. This is because the atom's final momentum is not the same as its initial momentum. The effect on the photon's wavelength is small, however.

The Doppler effect for atomic spectra is a purely realistic effect. It is a fundamental phenomenon that occurs when there is relative motion between a source and an observer. In the case of atomic spectra, the source is the atom emitting the photon and the observer is the detector measuring the photon's frequency.

The Doppler effect is a result of the change in wavelength of a wave due to the relative motion between the source and the observer. This change in wavelength results in a shift in the frequency of the wave, which is observed as a change in the spectral lines of the atomic spectra.

The formula for calculating the Doppler shift in atomic spectra does not depend on the mass of the atom, but rather on the velocity of the atom. This is because the mass of the atom does not affect the relative motion between the source and the observer. The only factor that affects the Doppler shift is the velocity of the atom, which determines the amount of wavelength shift.

Therefore, the Doppler effect in atomic spectra is a purely realistic effect that can be observed and measured in experiments. It is not an abstract or theoretical concept, but a physical phenomenon that can be explained and understood through scientific principles.

## 1. What is the Doppler effect for atomic spectra?

The Doppler effect for atomic spectra is a phenomenon in which the spectral lines of an atom appear to shift towards shorter or longer wavelengths, depending on the relative motion between the observer and the source of the light. This effect is caused by the motion of the atom, which changes the frequency of the emitted light.

## 2. Is the Doppler effect for atomic spectra a purely realistic effect?

No, the Doppler effect for atomic spectra is not purely realistic. It is a combination of both realistic and relativistic effects. Realistic effects are caused by the motion of the atom itself, while relativistic effects are caused by the motion of the observer relative to the atom.

## 3. How does the Doppler effect for atomic spectra affect the measurement of atomic properties?

The Doppler effect for atomic spectra can affect the measurement of atomic properties, such as the energy levels and transition frequencies of atoms. This effect must be taken into account when analyzing atomic spectra in order to accurately determine these properties.

## 4. Can the Doppler effect for atomic spectra be used to determine the motion of atoms?

Yes, the Doppler effect for atomic spectra can be used to determine the motion of atoms. By analyzing the shift in spectral lines, scientists can calculate the velocity and direction of an atom's motion.

## 5. How is the Doppler effect for atomic spectra applied in different fields of study?

The Doppler effect for atomic spectra is applied in various fields of study, such as astronomy, chemistry, and physics. In astronomy, it is used to study the motion of stars and galaxies. In chemistry, it is used to analyze the properties of atoms and molecules. In physics, it is used to study the movement of particles in experiments and to understand the behavior of matter at the atomic level.

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