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I have a very basic doubt in Bohr's Atomic Model. I just studied that an electron can go to any Energy State with in the atom, by getting relevant energy from photons. If an electron goes to 2nd Energy Level from Ground state,can it come back to 1st Energy State from it,then in ground state?? When I asked my teacher,he said....yes it can But my question is how?... Like, suppose the energy gap between ground and 1st energy level is 6eV. The electron got it somehow from an photon(can it get some no of photons to acquire this energy?,or it will just get 1?),and reaches 2nd energy state. Suppose this photon is a photon of Violet light. I observed in a YouTube video,when it come back from 2nd Energy level to the 1st, it emitted a different color of ray(not violet),then it emitted another color of ray(as photon),but not violet. My question is how it is possible?

Like, I gave it Violet colour photon and it emitted some different colors?

How?

If I eat rice,I can only vomit rice, Not any other kind of food, right?

Please explain me how it happens?

With some simple examples....

Thanks...

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    $\begingroup$ Consider a staircase of steps from ground floor to next higher floor. Toss a rubber ball up to a high step. Does the ball have to come back down directly the way it went up? Or is it possible to return to ground level via a cascade of steps? $\endgroup$
    – Ed V
    May 27, 2022 at 14:39
  • $\begingroup$ You should provide a link to the source of your confusion. How would one know what is this actually about? $\endgroup$
    – nasu
    May 27, 2022 at 17:14

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When an atom absorbs a photon and changes to an excited state that photon is destroyed and no longer exists. It is not stored in the atom in some way. The photon is destroyed and its energy goes into the increased energy of the atom.

Then when the atom decays to a lower energy state the energy released is used to create a brand new photon unrelated to the original photon. That's why the new photon can be different from the original one.

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Bohr's atomic energy model is outdated at present by the correct mathematical theory of quantum mechanics. Bohr's model was one of the stops on the way to the final theory , but it is an ad hoc model, not a mathematical theory with axioms etc rigorously leading to solutions of equations.

The quantization of the Bohr model is put in by hand , because in classical electromagnetism an electron orbiting a positive nucleus would fall on the nucleus because it would be radiating away electromagnetic energy. The Bohr model has as a law the quantization of angular momentum, which forces the orbits to be stable and changes in the orbit can happen by either absorption or decay to a photon, the hydrogen atom for example:

enter image description here

This is proven mathematically true in the strict theory of quantum mechanics, that is why the Bohr model has survived in current physics studies.

You ask

I observed in a YouTube video,when it come back from 2nd Energy level to the 1st, it emitted a different color of ray(not violet),then it emitted another color of ray(as photon),but not violet. My question is how it is possible?

Look at the image, that has the energy levels where the electron can be trapped. The photons needed to change energy level, either by absorption or by emmission will have different energies, and that is how that is possible. The incoming photon of the correct energy may take the electron to a high level, but the electron, depending on the energy level has levels below to cascade step wise, and the energy emitted will be different.( the color of the photon is connected to the energy by $E=hν$ ,$ν$ the frequency of the light seen from a large collection of excited hydrogen atoms, as in the image above).

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Suppose this photon is a photon of violet light. … when it come back from 2nd energy level to the 1st, it emitted a different color …(not violet),then it emitted another color …(as photon),but not violet. My question is how it is possible?

To make it more understandable and John Rennie's sentence "It is not stored in the atom in some way" more vivid, I'll explain it like this:

  • The photon is an energy quantum (an indivisible unit from its emission to its absorption) and has an electric and a magnetic field component. (how this can be proven experimentally, see here).
  • The electron also has an electric field and a magnetic field. Here we speak of its electric charge and its magnetic moment.
  • If a photon is emitted by an excited electron, then it is not surprising (from today's point of view) that the energy output is in the form of the two field components.

Photons can have very different energies. In their interaction with the electron, the state of their field components at the moment of interaction also plays a role (the two field components of the photon constantly change their field strengths). The electron, on the other hand, is subject to strict limitations as far as its energy states in the atomic compound are concerned. Therefore, an electron excited by a photon can fall from an nth energy level back to its ground energy level with different energy outputs.
It's like having two staircases and a wall next to each other. You take the wall with a jump upwards (perhaps with a trampoline). It doesn't matter whether you take the stairs with the few big steps or the stairs with the small steps or jump down the wall again. In the end you will have lost the energy gain.

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