# Photon is different from an eletron

1. May 28, 2007

### Ngom

Dear,
"when an electron jump from one state to an other one it does absorb or emmet an photon", For that it is not possible to caculate the life time of that photon? does anyone have any idea about the time that an electron can do by jumping from one state to an other one.

2. May 28, 2007

### marlon

When, in an atom, an electron changes energy state because the atom gets excited, a photon can be absorbed/emitted. You should realise that, in this situation of atoms getting excited, the entire atom absorbs the photon and NOT just the electron. As a matter of fact, a free electron has a continous energy distribution so clearly, the "jumping" you are referring to is not possible if we were just talking about an electron. Due to the fact that the electron is inside an atom, the energy levels of this electron are determined by its interaction with other electron and the atomic nucleus. In the latter case, the electronic energy distribution is discrete yielding the energy levels you are talking about.

marlon

3. May 28, 2007

### Ngom

right but when an atome change a energy state it emmeted or absord a photon it means that the distribution of the electron inside the atom have change, so what i am asking is that that photon what is it exactly, it is a kind of energy ditribution or it is a force that have been applied to change the energy distribution inside the atom.

4. May 28, 2007

### Astronuc

Staff Emeritus
A photon is a form of energy (electromagnetic). It has no rest mass, but does possess momentum, p = E/c, where E is the photon's energy.

Electron(s) and the nucleus form a system we call an atom. When an atom absorbs a photon, the energy and angular momentum of the electron changes (increases) within the atom and consequently the energy/angular momentum of the system changes. When a photon is emitted the energy and angular momentum decrease.

A photon imparts a force to an electron, by virtue of changing the momentum and energy of the electron. The electron 'jumps' between discrete (quantized) energy levels.

Crudely, if the moon were to gain mass (e.g. by a collision with a large mass), the moon's energy and momentum would change, and so would the energy/momentum of the earth/moon system change.

5. May 28, 2007