Need to understand about the photoelectric effect

Click For Summary

Discussion Overview

The discussion revolves around understanding the photoelectric effect, specifically focusing on the concepts of frequency and intensity of light, their relationship to the energy of emitted electrons, and the implications for experimental setups involving circuits.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that the equation E = hf pertains to the photon particle aspect of light, questioning how frequency (f) relates to the wave aspect.
  • It is suggested that increasing frequency leads to higher energy (E) for ejected electrons, which may increase their kinetic energy but not their quantity, assuming intensity remains constant.
  • Others argue that intensity, defined as the power per unit area, is responsible for the number of electrons ejected, while frequency affects their energy.
  • One participant seeks clarification on how an increase in intensity, while keeping frequency constant, results in more electrons being ejected, and how this relates to the wave aspect of light.
  • There is a discussion about the relationship between color and frequency, with some participants expressing confusion about how color, typically associated with waves, ties into the particle aspect of light.
  • Questions arise regarding the role of a battery in a circuit testing the photoelectric effect, with participants exploring whether it creates a voltage that aids in the movement of ejected electrons.

Areas of Agreement / Disagreement

Participants express varying views on the relationship between frequency, intensity, and the resulting electron emission, indicating that multiple competing perspectives remain. The discussion does not reach a consensus on these points.

Contextual Notes

Participants highlight the complexity of the wave-particle duality of light and its implications for understanding the photoelectric effect, noting that assumptions about intensity and frequency may lead to different interpretations of the results.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of physics, particularly those exploring concepts related to the photoelectric effect, wave-particle duality, and experimental setups in circuits.

sssddd
Messages
44
Reaction score
0
Hello my question involves what exactly is the frequency and intensity of the light. The E = hf applies to the photon particle aspect of light right? So where is f from, the wave aspect? Also increase f, which increases E makes the electrons eject faster in terms of kinetic energy right, but not increase in numbers. The intensity is what increases the number of electrons ejected but not speed? So is intensity part of the wave aspect? And how is it all related?
 
Physics news on Phys.org
sssddd said:
Hello my question involves what exactly is the frequency and intensity of the light.

it is what is set by the device emitting it. intensity is the power of radiation crossing a perpendicular surface (to the wave direction) per unit area. power is the time rate of change of the energy passing that surface.

The E=hf applies to the photon particle aspect of light right? So where is f from, the wave aspect?

f is determined by the color of the light. if it's white, there will be lot'sa different frequencies and lot'sa different electron energies.

Also increase f, which increases E makes the electrons eject faster in terms of kinetic energy right, but not increase in numbers.

if the intensity is constant, the number of electrons (per unit time) ejected will have to decrease (but there would be more average energy per electron) if f increases.

The intensity is what increases the number of electrons ejected but not speed?

all other parameters held constant, yes. but if the frequency changes and intensity held constant, the number of electrons emitted per unit time will change (inversely).
 
ok sounds like I'm on the right track. Just a little more, if frequency is constant. Increase in intensity the same as increase in power will eject more electrons. How does that work, more energy per length of time is distributed over each electrons, so more electrons ejected right. Now how does intensity connect with the wave aspect.

Also with frequency, could you please clarify a little more about the whole color thing, I thought color was waves and not particle. How does colors tie to the particle aspect. And if intensity is constant, and frequency increases, which is more energy per electron, how does frequency affect the numbers when intensity is constant. You said it decrease?

Oh by the way new question when this is tested in a circuit, why do u need a battery? Does the battery create a voltage that help electrons ejected go from cathode to anode bteween two plates like a capacitor? It will end up like a capacitor right
 
Last edited:
sssddd said:
ok sounds like I'm on the right track. Just a little more, if frequency is constant. Increase in intensity the same as increase in power will eject more electrons. How does that work, more energy per length of time is distributed over each electrons, so more electrons ejected right. Now how does intensity connect with the wave aspect.

increase the number of photons (of the same energy) and more energy is crossing your surface therefore intensity increases.

Also with frequency, could you please clarify a little more about the whole color thing, I thought color was waves and not particle. How does colors tie to the particle aspect.

it's a "wave-particle duality". this is what it is all about. waves with frequencies of [itex]f[/itex] are associated with particles with energy of [itex]E = h f[/itex].

And if intensity is constant, and frequency increases, which is more energy per electron, how does frequency affect the numbers when intensity is constant. You said it decrease?

if the intensity is constant and the frequency increases, the number of photons is less.

Oh by the way new question when this is tested in a circuit, why do u need a battery? Does the battery create a voltage that help electrons ejected go from cathode to anode bteween two plates like a capacitor? It will end up like a capacitor right

you need an adjustable DC voltage source to oppose the electrons emitted and you increase the voltage until the current from emission just barely gets to zero. the electon charge times the voltage is the energy of the electron. that gives you the "E" and the color gives you the "f" and from enough points (different colors, different energies) you can get "h".
 
Last edited:

Similar threads

  • · Replies 35 ·
2
Replies
35
Views
4K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 8 ·
Replies
8
Views
830
  • · Replies 1 ·
Replies
1
Views
1K
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K