What is Photoelectric: Definition and 440 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. S

    Concept about photoelectric effect

    I have trouble understanding these two separate questions: I know the answer for this one, it is (D). The KE of electron depends on the frequency of the light so since the frequency of the light does not change (I assume so), the KE wil stay the same. Increasing the intensity will increase the...
  2. mgcgian

    I Photoelectric effect: Saturation voltage

    Hi, I just got two inquiries: My understanding is that the saturation current is reached when the intensity of light is fixed, when the potential difference is at its positive maximum magnitude. Subsequently, whatever kinetic energy store of any photoelectrons, however deep within the metal's...
  3. 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...
  4. R

    B Is it possible to get the photoelectric effect in red color frequency?

    Is it possible to get the photoelectric effect in red color frequency?
  5. P

    I What were the real results of the photoelectric effect experiment?

    Pearson Physics 12 states: "When the light sources have the same intensity but different frequencies, they produce the same maximum current" However, Phet Simulation Photoelectric Effect seems to show that photocurrent changes with light frequency (eg see below for different photocurrents at...
  6. samy4408

    I Question about X-ray power emitted by the Coolidge tube

    hello i found this equation in a course about x rays , and i couldn't find it anywhere else they said that it is the theoretical expression of the energy spectrum , and dφ/dE is variation of the power emitted by the Coolidge tube as a function of the energy of the x ray. but i didn't understand...
  7. Aurora_b

    What is the common error when discussing the photoelectric effect?

    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...
  8. qnt200

    B Why is there now evidence of a lag time in the photoelectric effect?

    From: https://opentextbc.ca/universityphysicsv3openstax/chapter/photoelectric-effect/ "The photoelectric effect has three important characteristics that cannot be explained by classical physics: (1) the absence of a lag time, (2) the independence of the kinetic energy of photoelectrons on the...
  9. 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...
  10. docnet

    A basic question about Photoelectric effect

    The energy of a photon with wavelength ##\lambda=500nm## is given by the equation ##E_{photon}=h\nu=\frac{hc}{\lambda}##. ##E_{photon}=3.614\times10^-19 J=2.256eV## The kinetic energy of an ejected photo-electron is given by ##KE_{electron}=E_{photon}-Work## Using the given ##\lambda## and...
  11. 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...
  12. K

    Photoelectric effect and continuous energy function

    E=hf-W where W is a work function. However we know that electrons in an atom will be excited only when radiated with photons of n*f0 discrete number of frequencies. where E=hf-W is a continuous function. Is this because energy level is continuous within a conductor? If we think of only...
  13. AN630078

    Photoelectric Effect Graph and Work Function Questions

    1. a)I have plotted the graph on desmos and attached an image here. b i. The threshold frequency is equal to the x-intercept ~ 5.6*10^14 Hz ii. The work function is equal to the y-intercept ~ -3.75*10^19 J (would it be correct to state that this value is negative?) c. Convert to eV; 3.75*10^19...
  14. thaiqi

    Are there articles on Classical computation of the Photoelectric Effect?

    photoelectric effect is now explained in quantum idea. Why the classical model fails? Are there articles computing it in detail using classical model?
  15. J

    Photoelectric Effect questions to help my understanding

    Homework Statement:: This isn't homework, I didn't know exactly where to post my question so I thought it would be safest to post here. Relevant Equations:: N/a My questions are as follows: 1. When the voltage is increased to a certain value the current between the two plates(emitter plate)...
  16. 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?
  17. Manasan3010

    I Exploring the Physics of Photoelectric Cells: Electrons, Energy & Color

    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...
  18. Zeynaz

    Calculating Electron Emission and Reflection in the Photoelectric Effect

    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...
  19. G

    A Frequency threshold in the photoelectric effect

    The existence of a frequency threshold in the photoelectric effect is often regarded as the strongest objection to the wave theory. Because?
  20. G

    I Photoelectric Measurements & the Nature of Surfaces

    Why are photoelectric measurements sensitive to the nature of the photoelectric surface?
  21. B

    Photoelectric Effect versus Laser Stimulated Emission [Confused]

    Our teacher taught us "Laser" today and it made me confused. So Electron s energy in n=1 is around 13 eV (-13eV) and in n=2 is around -3.4 eV. Our teacher told us if we radiate a photon which has 9.6 eV energy (the difference energy of the first and second layer, n1 and n2, which is 13-3.4=9.6...
  22. Boltzman Oscillation

    Classical Book for research of the photoelectric effect?

    Hi, I am not sure if this is the right place to post this but i need help finding resources for the photoelectric effect? I need to write a research paper but I do not know what I could read. The paper is for an undergrad physics course so I don't need much detail, I just need to explain the...
  23. Sandeep T S

    I Energy of a Wave & the Photoelectric Effect: Is My Statement Correct?

    In classical electrodynamics energy of a wave is proportional to its intensity , this theory fails when Hertz did experiment on photoelectric effect. Is my statement is correct? If not correct me.
  24. J

    B Ultraviolet Catastrophe & the Photoelectric Effect

    Hi, Please could somebody verify if what I have understood about the UV catastrophe is along the correct lines. I used this hyperphysics link: (http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html) Is it saying that using classical physics an object like a pen should be emitting just as much...
  25. volnei_cipriano

    Photoelectric effect in the study of a luminous diode (LED)

    I have studied the operation of light Diodes in the basic electronics course in my graduation and I had a question! Light Diodes (LEDs) are semiconductor materials with P-N junctions and that when energized emit visible light. I understand that the process of light emission when applying a...
  26. Sandeep T S

    I Photoelectric effect questions: photon absorption and electron ejection....

    Is a photon fully absorbed by a electron in metal? Ejected electron is a free electron or bonded one? Is it possible to have a zero work function? If not why? I want to study about this detaily ,can you prefer some reference papers?
  27. Zahid Iftikhar

    I Ejection of Only one electron by a Photon in the Photoelectric effect

    Hi I am surprised to know why only one photon in photoelectric effect ejects one electron only. What if a high energy photon (not necessarily x-ray or gamma ray, which may cause Compton effect or pair production)hits the metal, say it has energy double or triple of that of the work function? Why...
  28. 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...
  29. B

    I Photons in the photoelectric efect

    What happens to the UV photons that strike the photovoltaic cell but do not take part in the photo electric efect, do thay reflect? apparently the best comercial solar cells are only 24% eficiant.
  30. Shivam

    Does the Photoelectric Effect Prove the Particle Nature of Light?

    It is said that photoelectric effect of light proves that light has particle nature, but which property is shown by light in the photoelectric effect which is also the property show by things having particle nature? Even in the photoelectric effect the energy is transferred in the form of wave...
  31. P

    Photoelectric effect, calculating work function

    Homework Statement (Given a voltage against frequency graph) Calculate the work function of Sodium and state any assumptions you have made. My question is, what assumptions have I made? Homework Equations hf = work function V = IR The Attempt at a Solution I know on a Voltage against...
  32. B

    A Photoelectric Effect via QED?

    Chapter 5 of this book: https://www.amazon.com/dp/0750633719/?tag=pfamazon01-20 as one can see in the table of contents preview, discusses the photoelectric effect starting from the first principles of quantum field theory developed in the earlier chapters. I can't find another qft book which...
  33. J

    Photoelectric current and a convex lens

    Homework Statement Homework EquationsThe Attempt at a Solution The photoelectric current is directly proportional to the intensity of the light falling on it . It will not depend on the focal length of the lens . When the lens of half the diameter is used , intensity is halved . This...
  34. 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...
  35. 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...
  36. D

    Question about the photoelectric effect

    1. The question asks why the photodiode is less than 100% efficient.2. hf=work function+KEmax 3.- I reckon this is as some light will not cause e to be emitted if the wavelength of the light is less the needed. -Or some photons will not hit any electron. Is this correct? Thinking about this...
  37. T

    Photoelectric effect , Superposition of sine waves

    Homework Statement In a photoelectric effect experiment, a monochromatic plane wave of light falls on a metal plate. The electric field in the light wave at a point near the plate varies according to E=E_0 \cos (\omega t). This results in a saturation current of 6 μA. If instead, the light wave...
  38. 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...
  39. 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...
  40. 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?
  41. A

    B Planck-Einstein relation and the Photoelectric Effect

    Hi everyone, I just have some confusion regarding Planck's and Einstein's equation. The following is an explanation of the photoelectric effect using Einsteins theory: Light is composed of photons. Each photon has energy hf and mass hf/c^2. When ultraviolet photons are brought to rest by zinc...
  42. T

    Kinetic energy of recoil atom in the photoelectric effect

    Homework Statement In the photoelectric effect it is generalley assumed that all the energy is given as kinetic energy to the electron while the atom is neglected. Do not neglect the recoil kinetic energy of the atom and calculate the kinetic energy of the photoelectron and the ionized atom and...
  43. CarmenGonzalez

    [Nuclear Physics] photoelectric peak

    Homework Statement The material of which a gaseous detector is constituted has the following values of mass attenuation coefficients for a given photon energy: Rayleigh: 0.0084 cm2 / g Photoelectric: 0.071 cm2 / g Compton: 0.022 cm 2 / g Calculate the relative intensity of the photoelectric...
  44. F

    I Confusion with the Photoelectric Experiment

    I've always struggled with circuits and never got a firm handle (hence the very basic questions...please bear with me). What I understand of Lenard's Experiment: Light hits the emitter plate and some electrons fly off. ...lol yeah that's about it. Here is one major confusion that I have: Not...
  45. mertcan

    Photoelectric effect -- direction of the electron's trajectory

    Hi, I would like express that I really tried to dig something about the formula related to electron direction in photoelectric effect, but I could not find. Also I have seen that electron direction in photoelectric effect is not known according to some sites in internet. So, ıs it real that in...
  46. 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...
  47. *now*

    Photoelectric effect calculation

    Photoelectric effect 1. Homework Statement A metal surface is illuminated with monochromatic light and it becomes charged to a steady positive potential of 1.0V relative to its surroundings. The work function energy of the metal surface is 3.0eV, the electron charge is 1.6 x 10-19 C. Calculate...
  48. R

    B About electrons and the photoelectric effect

    I understand that electrons can be released from a material, such as metal, through the photoelectric effect. I also understand that some of them might "re-attach" themselves to the metal. For practical uses, it sounds like the electrons would be re-captured in some way, but for the electrons...
  49. C

    Does the photoelectric effect eventually stop?

    Assume that a light shining on a metal initially resulted in electrons being emitted from the surface of the metal due to the photoelectric effect. If the light is left on indefinitely, will the emission of electrons eventually cease? (Assume the metal is insulated on all surfaces apart from the...
  50. C

    Interpreting I-V graphs in Photoelectric effect

    Homework Statement In photoelectric effect I-V graphs, for the same intensity but with different light frequencies (f2>f1), the I-V graph has the same max photocurrent but |Vs2| > |Vs1|. If we concentrate between the cutoff and the saturation regions of the I-V graph, we can see that at any...