Photoelectric Effect and energy

In summary, the maximum energy for a photoelectron is determined by the energy of the photon, and not by the original energy of the electron.
  • #1
MHD93
93
0
Hello

Before a photon hits an electron, the electron originally had a kinetic energy, if f = f0 we know that
Kmax = hf -hf0 = zero

shouldn't the electron's kinetic energy increase the photon hits it? not the converse?
 
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  • #2
Kmax = hf -hf0 = zero

Sorry Mohammad, have you misquoted this? Photoelectrons have a range of energies from zero up to Emax = hν - φ, where φ is the work function of the metal. In other words it's just the opposite of what has been said - the maximum energy is determined by the energy of the photon, and not by the original energy of the electron.
 
  • #3
Bill_K said:
Sorry Mohammad, have you misquoted this? Photoelectrons have a range of energies from zero up to Emax = hν - φ, where φ is the work function of the metal. In other words it's just the opposite of what has been said - the maximum energy is determined by the energy of the photon, and not by the original energy of the electron.

It's what I ask..
Why isn't the maximum energy is the energy of the photon added to the original electron's energy
 
  • #4
Oh OK, that's because this is the maximum energy. Electrons in the metal have a maximum energy, EF the Fermi energy, which is an amount φ below the vacuum outside. So hν - φ is the maximum energy the emitted photoelectron can have. If the photoelectron came from below the Fermi level, then of course its energy will be less.
 
  • #5
Mohammad_93 said:
It's what I ask..
Why isn't the maximum energy is the energy of the photon added to the original electron's energy
It is, but that's not the whole picture. As explained by Bill, there's an additional potential energy barrier that needs to be overcome. The maximum KE of the Photoelectron is therefore equal to its original energy (EF) + the photon's energy (hv) - the final potential energy (Evac).

KE(max) = hv - (Evac - EF) = hv - φ

φ is called the Work Function, and if you define, φ = hv0, that gives you: KE(max) = hv - hv0
 
  • #6
THanks.. that's given me the whole picture, helpful.

##
 
  • #7
THanks.. that's given me the whole picture, helpful.

##
 

What is the photoelectric effect?

The photoelectric effect is a phenomenon in which electrons are emitted from a material when it is exposed to electromagnetic radiation, such as light.

What is the relationship between the photoelectric effect and energy?

The photoelectric effect demonstrates the particle nature of light, showing that light is made up of discrete packets of energy called photons. When a photon strikes a material, it transfers its energy to an electron, causing it to be emitted from the material. This energy transfer is the basis of the photoelectric effect.

What factors affect the amount of energy transferred in the photoelectric effect?

The amount of energy transferred in the photoelectric effect depends on the frequency of the incident light, the work function of the material, and the number of photons striking the material. Higher frequency light, lower work function, and more photons all result in a greater amount of energy being transferred.

Can the photoelectric effect be explained by classical physics?

No, the photoelectric effect cannot be explained by classical physics. Classical physics predicts that the energy of the electrons emitted from a material should increase with the intensity of the incident light, but in reality, the energy of the electrons is dependent on the frequency of the light. This discrepancy led to the development of quantum mechanics.

What are some applications of the photoelectric effect?

The photoelectric effect has many practical applications, including solar panels, photodiodes, and photocells. It is also used in devices such as photocopiers, barcode scanners, and digital cameras. Additionally, the photoelectric effect is used in scientific research to study the properties of materials and to better understand the behavior of light.

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