Photoelectric effect Definition and 47 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. in2infinity

    B The wave solution to the Photoelectric effect

    I was recently examining the relationship between the work function of a material and its threshold wavelength. It was clear to me that the relationship is expressed as: (λW)² = c/2 Where λ is the threshold wavelength, W is the work function, and c is the speed of light. However, I am unable...
  2. Aurora_b

    Photoelectric effect problem

    I would believe the last statement if Intensity only depended on N but it also depends on the frequency f. Now if Intensity depends on f we can also find a relationship between KE_max and Intensity by substituting from eqn 2) in eqn 1) KE_max = IA/N - W So if KE_max depends on f and I depends...
  3. B

    Photoelectric Effect Classical Breakdown

    So I'm kind of confused about how to interpret the question and the idea of there being a small enough ##\tau## for the classical picture to break down. I started with the max KE eqn: ##KE_{max} = E_{incoming} - \phi## I suppose ##E_{incoming}## is the power (W) times time and that is also...
  4. 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...
  5. Rongeet Banerjee

    Definition of Cathode

    We know anode=oxidation=loss of electrons and cathode=reduction=gain of electrons but in the photoelectric effect the electrons are gained at the anode and lost at the cathode of the discharge tube? References: Anode, Cathode, Oxidation, Reduction
  6. T

    A Photoelectric effect at metal junctions

    Any idea about difference in photoelectric effect between a piece of pure metal and that metal connected at one end with another metal. Would the work function of the metal with photoelectric effect differ in the latter case?
  7. Manasan3010

    I Why an electron gets knocked out of an atom instead of going to a higher energy level

    In this article, writer says that when atom is hit by photon it gets excited and expelled out of atom and this can be used to form images. My questions are: Why didn't the electrons get to a higher energy level, instead of getting knocked out? How do we find the color(frequency of wave) using...
  8. Zeynaz

    Photoelectric effect question

    The full questions is in the picture. I already solved a) and found 5.6E14 electrons per second For b) i first found the power of the light but just multiplying the intensity with the area: (6.0 W/m2)(3.5E-4 m^2) = 0.0021 W Then I tried to use the voltage from the graph but i am not sure which...
  9. 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...
  10. MeAndMyLucidLife

    Photo-current and Intensity of light

    Homework Statement If the frequency and intensity of a light source are both doubled, show that the saturation photo-current remains almost the same. 2. Relevant Graph The Attempt at a Solution...
  11. Safder Aree

    How to approach this photoelectric effect question

    I am currently taking my first Quantum Mechanics course and was given this problem in a practice set(we are supposed to refer to old intro textbooks). We haven't covered the photoelectric effect (just theory) much in class and reading through other textbooks, I wasn't able to find any similar...
  12. F

    Saturation voltage for photoelectric current

    Hi, I was wondering about saturation current in the photoelectric effect. It is clear to me that for a sufficiently large accelerating potential all of the electrons are gathered by the collecting electrode. Since it is all of them, there cannot be more, and the current won't change if the...
  13. spareine

    Is the photoelectric effect in a photocell reversible?

    Is the photoelectric effect in a photocell reversible? Suppose both the cathode and the anode of a photocell are from cesium. The anode and the cathode are externally (outside the photocell) connected by a copper wire. Cesium has a threshold frequency of 470 THz. The cathode is illuminated with...
  14. G Cooke

    Conservation of electrical energy on a conductor

    I'm having trouble seeing how electric potential energy production on a conductor follows conservation of energy. Let's use the photoelectric effect as an example. A photon with energy E = hν strikes a conductor, ejecting a photoelectron with a maximum kinetic energy of hν - φ. Assuming the...
  15. E

    Photoelectric Effect

    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...
  16. F

    Does this formula exist? (ν' = En/hc)

    ν' = En/hc ? ν' is the wavelenght's number (in electromagnatique radiation) where ν' = 1/λ if so, how do we get it ?
  17. C

    Does charging metal negatively decrease the work function?

    Since positive charge on the photocatode increases work function of electrons, does charging metal photocatode negatively decrease work function? If not, why?
  18. Pushoam

    The effect on a photocurrent of reducing the frequency of photons

    Homework Statement Homework Equations The Attempt at a Solution As frequency is decreased to threshold, no. of emitted electrons will remain same, but their maximum kinetic energy will decrease. So, the current should decrease slowly. For frequency less than the threshold frequency, no...
  19. 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^2 The 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...
  20. Z

    Photoelectric Effect, Light Intensity and Stopping Voltage

    In a physics investigation we were required to use a Photo-Electric Effect Instrument (Shown in the attached pdf file), which was able to measure the current produced via the photoelectric effect. One of the objectives of the investigation was to alter the aperture size, and hence intensity of...
  21. lawlieto

    I Are any electrons ejected below the threshold frequency?

    I've been reading about the photoelectric effect, and something got me thinking. If the frequency of light shone onto the metal is below the threshold frequency, no electrons are liberated from the surface of the metal, since electrons absorb quanta of energy, so if that light is shone for a...
  22. C

    Photoelectric effect : retarding potential with back current

    In the experiment of the determination of ##h## using the photoelectric effect produced by light emitted by led's there is the systematic problem of the "dark current" or "back current", i.e. the current caused by photoelectric effect on the anode of the system which is used in the expreriment...
  23. tom.stoer

    I Interpretation of the photoelectric effect

    The photoelectric effect is usually presented as an example disproving classical electromagnetism as viable model for interaction of light with matter and as evidence of quantization of energy in the electromagnetic field, i.e. the existence of photons. I would like to discuss a thought based on...
  24. W

    Releasing Electrons with a color filter!

    Homework Statement Simple question we have to answer: (Physics) How do I release the electrons from the cathode with a color filter? (The so called Photoelectric effect) Homework Equations none The Attempt at a Solution[/B] Here we have a conflict , the so called wave-particle duality...
  25. Bloopy

    B Einstein's Photoelectric Equation and its graph

    According to the equation, the graph of kinetic energy of emitted photoelectrons from a metal vs the frequency of incident radiation gives a straight line. My doubt is, what factors does the slope of this line depend on? I think it depends on the nature of metal used. Correct me if I am wrong.
  26. P

    What properties of waves causes the photoelectric effect

    What properties of waves caused the photoelectric effect to indicate the fact that light was quantized. Why couldn't it be explained by light waves being emitted at the same frequency. I am a little confused about why light couldn't still be a wave. Couldn't the photoelectric effect be explained...
  27. Elvis 123456789

    Question concerning photoelectric effect lab

    This isn't really a homework question but I do have to know it for my lab report so I figure this is a good place to post it. So for my lab we had the setup that is displayed in the picture attachments. My question deals specifically with step #9 of the lab instructions. I'm assuming that the...
  28. A. Neumaier

    I History of the modeling of light

    That a quantum detector responds to classical light precisely according to Einstein's formulas for the photoeffect was already shown briefly in 1926 (the year the Schroedinger equation was born) by Wentzel, and was described in full detail in 1964 (when the development of the laser strongly...
  29. EngPhy

    A Effect of visible light on conductivity

    Are metals better conductors in the presence of visible light? Considering photons in visible spectrum are not energetic enough to induce emission from a metal surface but they do cause the ejection of 'conduction electrons' which are bound to the metal by a few electron volts.
  30. Supitha

    B 2 questions about the photo electric effect

    How can explain the difference of these red dots? Red line = Green line ?. How to explain it?
  31. S

    Why do we have a saturation current in photoelectric effect?

    I had this question popped into my mind when I was reading this topic one day. In the photoelectric experiment, when light, having frequency greater than the threshold frequency, falls on a metal, electrons are emitted. Since electrons emitted are of different energies (I presume it's because...
  32. 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...
  33. S

    Desired properties for a solar cell

    Elements like Silicon, Germanium and Gallium can be used to make solar cells but platinum can not be used. What is the exact reason? Is it related to threshold frequency? Tried to search for the answer through many sources, but couldn't get a satisfactory one. Your views and answers are really...
  34. E

    An Inexpensive Hobbyist Photoelectric Effect Lab Kit

    What materials and equipment would be needed to for a hobbyist photoelectric effect lab kit? If possible, trying to keep this within a budget of $50. (Cheaper if feasible).
  35. E

    Questions on photoelectric effect

    Hello! First of all, this is my first post here. I hope it's on the right thread. I managed to answer most of the questions, but I think at least some of them are wrong (for example, d)). Any help would be really appreciated. Homework Statement A monochromatic light beam of wavelength λ=500nm...
  36. bcrowell

    Photoelectric effect: V classically independent of intensity

    In the photoelectric effect, we observe that the stopping potential is independent of the intensity of the light. This is readily explained by the photon hypothesis. One often sees the statement that in "the classical theory," the stopping potential should increase with intensity. What...
  37. A

    Compton effect and photoelectric effect

    Is the Compton effect more supportive of the photon theory of light than the photoelectric effect?
  38. 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...
  39. 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...
  40. A

    Photoelectric effect and Compton scattering

    Homework Statement A photon with of 13600eV energy interacts with a hydrogen atom at rest and ejects the electron (photoelectrically) in the direction in which the photon was travelling. If 13.6 eV is required to eject the electron, find the speed of the photoelectron and the momentum and...
  41. MASmith

    Determining Planck's Constant With Photoelectric Effect

    Homework Statement I'm trying to determine Planck's Constant through an experiment with the Photoelectric Effect, however, the equations I'm given and the data I've collected are not getting me to the 6.63e-34 that I need to be at. I'm graphing Stopping Potential (V) vs 1/λ and then using the...
  42. G

    Photoelectric Effect - Laboration

    Homework Statement "During a laboratory experiment with photoelectric effect, a metal plate is irradiated with light. The voltage that completely stops the beam of electrons is then measured. When the wavelength is 546 nm, the voltage is 0,38 V. When the wavelength is 410 nm, the voltage is...
  43. D

    E=hf interpretation

    I know what the letters mean, E = Energy of the photon, h = Planck's constant, f = frequency of the photon. But what does it mean for a particle to have a frequency, something that I'd associate with a wave. And what can you think Planck's constant is representing? Any replies would be much...
  44. J

    What happens when you remove an excessive amount of electrons.

    Lets take a simple water molecule for example. You can use the photoelectric effect to remove electrons from a molecule. As a thought experiment, let's say you have a contained single water molecule in a vacuum with no impurities. Perfect Vacuum. If you use the Photoelectric effect and beam...
  45. Q

    Photoelectric effect experiment: is current proportional to charging time?

    I'm not really sure where to put this question, but definitely this is just an introductory physics coursework. Let me refresh you first with the basics of the photoelectric effect. We all know that in the photoelectric effect the stopping voltage is just the kinetic energy obtained by the...
  46. T

    Saturation current on photoelectric effect

    From the post and [Broken] I have some idea on why does a higher potential different will not...
  47. Salvador

    Photoelectric current

    Hi, how could i calculate the current I would get from the photoelectric effect, so that the end result would be in amps? If I have a certain lightsource or source of powerful enough em radiation to conduct the photoelectric effect , how could I calculate the intensity needed for given current ...