What is Photoelectrons: Definition and 25 Discussions

The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid state and quantum chemistry to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission.
The experimental results disagree with classical electromagnetism, which predicts that continuous light waves transfer energy to electrons, which would then be emitted when they accumulate enough energy. An alteration in the intensity of light would theoretically change the kinetic energy of the emitted electrons, with sufficiently dim light resulting in a delayed emission. The experimental results instead show that electrons are dislodged only when the light exceeds a certain frequency—regardless of the light's intensity or duration of exposure. Because a low-frequency beam at a high intensity could not build up the energy required to produce photoelectrons like it would have if light's energy was coming from a continuous wave, Albert Einstein proposed that a beam of light is not a wave propagating through space, but a swarm of discrete energy packets, known as photons.
Emission of conduction electrons from typical metals requires a few electron-volt (eV) light quanta, corresponding to short-wavelength visible or ultraviolet light. In extreme cases, emissions are induced with photons approaching zero energy, like in systems with negative electron affinity and the emission from excited states, or a few hundred keV photons for core electrons in elements with a high atomic number. Study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of wave–particle duality. Other phenomena where light affects the movement of electric charges include the photoconductive effect, the photovoltaic effect, and the photoelectrochemical effect.

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  1. P

    I Question about the Photoelectric Effect and the Work Function of a Metal

    By the results of the photoelectric effect experiment, the photoelectric effect does not occur at all if the frequency of the light source is below a certain value. We have the Work Function for a metal. Why when the energy of the photons of the light source is W/2, we don't have the...
  2. R

    I Some questions about the photoelectric experiment

    Background: self-studying. Very confused. Here are some initial questions I have about the photoelectric experiment. Some more may pop up later. 1. The book says we know photons exist due to energy considerations (such as emission or absorption). They also say that this photon energy is...
  3. B

    Photoelectrons and Planck's constant

    Attempt: I was thinking of finding the slope of the graph but I only know the values for x = 10, y = 3 and y = 0. And without the y-intercept, I don't know the work function and can't solve for h. If you can't see from the picture, the last co-ordinate is (10,3) and the x-axis is measured in f...
  4. T

    I Photoelectric absorption and low energy electron absorption

    I have am currently reading Radiation Detection and Measurement, by Gleen F.Knoll, and in chapter 10 page 309. And have come across something that is causing a bit of confusion, for context the chapter is on gamma ray spectroscopy. So in the text it say's 'Thus the effect of photoelectric...
  5. C

    How Does Light Intensity and Frequency Affect Photoelectron Emission?

    Homework Statement Use Max Planck’s quantum theory to explain the following behavior of photoelectrons. a) Low-intensity light does not release any photoelectrons. What will happen if the light is made brighter? Explain your reasoning b) Low-intensity light releases photoelectrons. What...
  6. E

    Photoelectric Effect: Find K.E. of Photoelectron in Air, Cs-137

    Homework Statement The gamma photon emitted by the nucleus of the cesium isotope with 137 mass number is absorbed with photoeffect. The absorbing medium is air, assume the work function to be 34 ev. What will be the kinetic energy of the photoelectron in eV? Homework Equations hf=K+Φ The...
  7. S

    How can I find the maximum KE of the photoelectrons?

    Homework Statement I don't know how to do Question 2 part C. Homework Equations I know that E=hf and I know the photoelectric equation: hf = work function + 1/2mv^2The Attempt at a Solution I honestly don't have a clue how to do part c of question 2. I think it involves one of the two...
  8. manaXmizery

    Kinetic energy of the photoelectrons

    Homework Statement A beam of ultraviolet light with wavelength of 200 nm is incident on a metal whose work function is 3.0 eV. Note that this metal is applied with +1.0 V with respect to the ground. Determine the largest kinetic energy of the photoelectrons generated in this process. Homework...
  9. D

    A About X-ray Photoelectron Spectroscopy

    Hello, I am trying to create peak models for some XPS spectra. I have a decent intuition of the chemistry of the samples, and I obtain really good residual standard deviation values for the modeled data; however, some of the FWHM of the modeled oxidized species (C and P) on the narrow scans are...
  10. E

    Number of photoelectrons liberated

    Homework Statement A beam of light has two wavelengths λ1 (A°, i.e. angstrom) and λ2 with total intensity of I (W/m2) equally distributed amongst the two wavelengths. The beam falls normally on an area A m2 of a clean metallic surface of work function φ (eV). Assume that there is no loss of...
  11. M

    Photoelectron to electron hole pair doubts

    Hi, I have a couple of questions on photoelectrons. When a photoelectron of about 3-eV (varies) interacts within 0.2-um depletion region of silicon, what happens? I know, it will generate an electron-hole pair with an efficiency of 1 for 3.6-eV photoelectron. But what happens if the...
  12. X

    Ionization & photoelectrons in x-ray solid state detectors

    As far as i understand, this is the principle of solid state x-ray detectors: 1. A photon of energy E enters the detector and goes through photoelectric absorption 2. As a result a photoelectron with energy (E - Φ) is ejected, where Φ is the binding energy required to eject the photoelectron...
  13. ryanuser

    Why Does the Kinetic Energy of Photoelectrons Rise Up to a Maximum?

    Hi Why kinetic energy of photoelectrons rise up to a maximum? Thanks
  14. CAH

    Electron-Electron Interaction & Photon-Electron Interaction?

    I learned that photons can exite and ionize electrons in an atom, bring them to higher energy level etc. However I've seen a few questions on electrons bombarding electrons in an atom and exiting the orbital electrons to higher energy level. Is this the same as the photoelectric effect when...
  15. CAH

    Electrons absorb exact energy photons so how is Ek possible

    Hello! I've read that electrons can only absorb photons of exactly the right amount of energy to move to a higher energy level, if its to little or too much then it doesn't absorb it at all, so my question: How can electrons be liberated from an atom with Kinetic energy when they can't absorb...
  16. C

    Effects of frequency on rate of emission of photoelectrons

    Light of constant intensity is incident on a metal surface, causing electrons to be emitted. State and explain why the rate of emission of electrons changes as the frequency of the incident light is increased. My answer: As frequency increases, energy of photons also increases, so more energy...
  17. U

    Photoelectrons ejecting from Cs metal

    Homework Statement A small piece of cesium metal (W=1.9eV) is kept at a distance of 20cm from a large metal plate having a charge density of 1.0*10^-9 C m^-2 on the surface facing the cesium piece. A monochromatic light of wavelength 400nm is incident on the cesium piece. Find the minimum and...
  18. L

    Colour of light producing photoelectrons?

    Homework Statement a) calculate the energy, in joules, of a quantum of light with a wavelength of 590 nm. b)will this colour be able to produce photoelectrons from the surface of a metal with a work function of 3.0 eV? Explain your reasoning. Homework Equations f=c/λ E=fh ek=hf-W The Attempt...
  19. S

    Effect of Light Intensity on Photoelectron Kinetic Energy and Emission Rate

    Homework Statement A metal gives off photoelectrons with maximum kinetic energy Kmax at the rate of N per second when a beam of light of wavelength λ shines on it. How will Kmax and N change if the intensity (brightness) of light is doubled? Assume 100% efficiency. Homework Equations...
  20. X

    What is the work function of the metal?

    Light of 300 nm wavelength strikes a metal plate, and photoelectrons are produced moving as fast of 0.002c. What is the work function of the metal?
  21. E

    How Many Photoelectrons Are Ejected Per Second in This Experiment?

    1. To make it easier I just scanned it http://farm3.static.flickr.com/2062/2457086181_c2a13b6077_o.jpg" I am supposed to find how many photoelectrons are ejected per second in the experiment represented by the graph. 2. See link 3. Also see link, all of my work so far is there...
  22. A

    Light intensity, Max KE of photoelectrons

    Please check to see if my solution is correct: Question: If a light source were increased by a factor of 2 in intensity, what would happen to the value of KE_max of each photoelectron? My solution: KE_max would stay the same because increasing the intesity by a factor of two would only...
  23. D

    Threshold wavelength photoelectrons

    With what speed will the fastest photoelectrons be emitted from a surface wih threshold wavelength of 600nm when the surface is illuminated with light of wavelength of 400nm?
  24. W

    Quantum Physics and photoelectrons

    here are another questions,I need someone to help me! (1)A metal work a work function of 2.40 eV is illuminated with a beam of monochromatic light.The stopping potential for the emmited electrons is 2.50 V.What is the wavelength of the light in nanometer? (2)What is the lowest frequency of...
  25. S

    Can anyone help me with this problem regarding photoelectrons?

    Hi, I am new to this forum, doing A level physics, and have problems with photoelectrons and quanta etc... This is a question I would like help with: "Experiments on the photoelectric effect show that: -the kinetic energy of photoelectrons released depends upon the frequency of the...