You are Here: Home >< Physics

# Excitation of electrons Watch

1. When an incident electron collides with an orbital electron it becomes excited, that if there was enough energy. But if this energy is higher than the energy needed to excite the electron does it still get excited, as the absorption of photon on electrons stars that the photon has to be the exact amount of energy for an electron to be excited, no lower or higher value causes the electrons to be exited in photon absorption, is this the case with collision of electrons?

Posted from TSR Mobile
2. Anyone?

Posted from TSR Mobile
3. (Original post by Jimmy20002012)
When an incident electron collides with an orbital electron it becomes excited, that if there was enough energy. But if this energy is higher than the energy needed to excite the electron does it still get excited, as the absorption of photon on electrons stars that the photon has to be the exact amount of energy for an electron to be excited, no lower or higher value causes the electrons to be exited in photon absorption, is this the case with collision of electrons?

Posted from TSR Mobile
No, electrons can collide with an atom and give up part of their energy in exciting an orbital electron. The remaining energy (kinetic) is kept by the electron. It can then go on to strike another atom and excite more orbital electrons. This is how an electron can lose its energy when it travels through materials. It makes a number of collisions with molecules/atoms and loses its energy gradually.

The case of a photon colliding with an atom is more complicated. In one scenario the photon gives up all its energy to the orbital electron and then vanishes. In this case the photon needs exactly the right amount of energy to excite the electron.
It is possible (though this is not studied at A Level) for a photon to give up only part of its energy in a collision with an atom. In this case the photon's frequency (and wavelength) is changed, as photon energy = hf
Look up "Compton Effect", or "Compton Scattering".
http://hyperphysics.phy-astr.gsu.edu.../comptint.html
4. (Original post by Jimmy20002012)
When an incident electron collides with an orbital electron it becomes excited, that if there was enough energy. But if this energy is higher than the energy needed to excite the electron does it still get excited, as the absorption of photon on electrons stars that the photon has to be the exact amount of energy for an electron to be excited, no lower or higher value causes the electrons to be exited in photon absorption, is this the case with collision of electrons?

Posted from TSR Mobile
Basic conservation of energy. It will get excited and like the previous post said gain kinetic energy.
5. (Original post by Stonebridge)
No, electrons can collide with an atom and give up part of their energy in exciting an orbital electron. The remaining energy (kinetic) is kept by the electron. It can then go on to strike another atom and excite more orbital electrons. This is how an electron can lose its energy when it travels through materials. It makes a number of collisions with molecules/atoms and loses its energy gradually.

The case of a photon colliding with an atom is more complicated. In one scenario the photon gives up all its energy to the orbital electron and then vanishes. In this case the photon needs exactly the right amount of energy to excite the electron.
It is possible (though this is not studied at A Level) for a photon to give up only part of its energy in a collision with an atom. In this case the photon's frequency (and wavelength) is changed, as photon energy = hf
Look up "Compton Effect", or "Compton Scattering".
http://hyperphysics.phy-astr.gsu.edu.../comptint.html
Okay just to clarify, when an electron is incident on an orbital electron it gives it energy of hf, so the electron is excited and moves up to a higher energy level, if this energy is sufficient enough it can cause ionization where the orbital electron will be released from the atom.

With photon absorption, where photons depends on frequency as this provides energy according to the equation of E=hf. There is a one to one interaction between an photon and the electron. The photon must have the exact amount of energy in order to excite the electron, thus the photon must be the same as the intial and final energy difference of the electrons. All of the electrons absorb the energy of hf, and these electrons occupy discrete energy levels

Posted from TSR Mobile
6. (Original post by Jimmy20002012)
Okay just to clarify, when an electron is incident on an orbital electron it gives it energy of hf, so the electron is excited and moves up to a higher energy level, if this energy is sufficient enough it can cause ionization where the orbital electron will be released from the atom.

With photon absorption, where photons depends on frequency as this provides energy according to the equation of E=hf. There is a one to one interaction between an photon and the electron. The photon must have the exact amount of energy in order to excite the electron, thus the photon must be the same as the intial and final energy difference of the electrons. All of the electrons absorb the energy of hf, and these electrons occupy discrete energy levels

Posted from TSR Mobile
First paragraph.
No need for hf
That's the energy of a photon, not an electron in this case.

Otherwise ok.

Para 2
E=hf for photon is correct here.
Yes the photon has to give up all its energy in this case so it must have energy equal to the exact difference of energy between the electron's initial and final energy level.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 16, 2013
Today on TSR

### Medicine offers rolling in

Which unis have sent theirs?

### I hate Christmas

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.