What does the photoelectric effect demonstrate

In summary: If it's a more advanced class, then "the dual nature of light."In summary, the photoelectric effect, as demonstrated by Einstein, can be used to argue for both the particle and wave nature of light. While it historically played a role in the debate, it ultimately shows the discrete energy nature of electromagnetic radiation and suggests the possibility of the dual nature of light. However, the answer may vary depending on the level of the class and the specific question being asked.
  • #1
Chen
977
1
In an exam today the teacher asked "What does the photoelectric effect demonstrate" and the answers were "The wave nature of light", "The particle nature of light", "The dual nature of light" (i.e both)" and "Neither".

I answered that it demonstrates the dual nature of light, but she insists that it is only the particle nature of it. I think she is wrong, because when analyzing the effect we talk about the photon's energy which is equal to [tex]h\nu [/tex], but [tex]\nu [/tex] is the frequency of light and that is clearly a wave property.
 
Physics news on Phys.org
  • #2
Chen said:
In an exam today the teacher asked "What does the photoelectric effect demonstrate" and the answers were "The wave nature of light", "The particle nature of light", "The dual nature of light" (i.e both)" and "Neither".

I answered that it demonstrates the dual nature of light, but she insists that it is only the particle nature of it. I think she is wrong, because when analyzing the effect we talk about the photon's energy which is equal to [tex]h\nu [/tex], but [tex]\nu [/tex] is the frequency of light and that is clearly a wave property.
Isn't it talking of light in terms of photons, which show a particle behaviour rather than a wavelike behaviour...
 
  • #3
Chen,

Well, it wasn't a very fair question. If I had asked it on a test, I think I would have given credit for both answers.

That said, I think the pure particle answer is more right than the wave particle duality anwer. Frequency isn't just a wave property; it's a property of any vibration. So, the photoelectric effect could be explained with vibrating particles. It can't be explained with a wave.
 
  • #4
But we define the energy of each photon as [tex]h\nu [/tex] and that is a wave property. If I throw balls at a wall one a at a time I can't talk about their wave frequency, can I?

(Just saw your post) I agree that it's a "trick question". If the question was "Which behaviour of light does the effect prove", the answer would have been particle behaviour of course. But that wasn't the question...
 
  • #5
Chen said:
But we define the energy of each photon as [tex]h\nu [/tex] and that is a wave property. If I throw balls at a wall one a at a time I can't talk about their wave frequency, can I?

But that what makes it NOT a wave property. The energy of a classical wave is DEFINED as NOT being a function of frequency, but rather AMPLITUDE. The frequency only comes in as the "power" of the energy being transfered. The "frequency" involved in [tex]h\nu[/tex] involves the oscillation of the E-field within the "energy packet". This isn't a wave that most of us are familiar with.

So the photoelectric effect is one example of the discrete energy nature of EM radiation. So I would side with your teacher in this case.

Zz.
 
  • #6
That's a bad question. Because in my mind, the explanation offered for the photoelectric effective effectively demonstrates the dual nature of light. Since light had already been thought of as a wave, when this experiment was explained by Einstein, it showed that light could be thought of as both a particle and a wave.
 
  • #7
What's the wave amplitude of a photon?
 
  • #8
The photoelectric effect demonstrates the particle nature of light as it shows that light arrives in little packets called photons. in calssical wave nature the light could knock an electron out of orbit just by the accumulation of energy from one wave, but the photoelectric effect shows the light has to be above a certain frequency to free the electron thus dismissing the classical idea.
 
  • #9
Oh, tight spot!

Historically, the photoelectric effect played an important role in the debate about the wave vs particle nature of light, and this history is a ghost at our banquet (and is echoed in how teachers write exam questions). Also, ZapperZ well summarises a common view.

However, on balance I think Chen should have been sharp enough to intuit (?) what the teacher was looking for - after all, isn't the secret to getting good marks in a multiple-choice test to ask "now just what is the test-setter looking for here?"?

It reminds me of the student who was flunked for answering a question about using a barometer to measure the height of a very tall building (she answered, in effect, drop it from the top and measure how long it takes to smash into the footpath below). But that's for a different day ... :wink:
 
  • #10
Indeed, Einstien's Photoelectric Effect does show the possiblity of the dual nature of light. Most commonly observed phenomena with light can be explained by waves. But the photoelectric effect suggested a particle nature for light. This effect shows that light behaves as particles.I really think the answer depends on what level class you are taking. If it's an intro physics class, then I would have answered, "the particle nature of light."
 
Last edited:

1. What is the photoelectric effect?

The photoelectric effect is the phenomenon where photons (particles of light) are able to eject electrons from a material when it is exposed to light. This was first observed by Albert Einstein in 1905 and was crucial in understanding the dual nature of light as both a wave and a particle.

2. How does the photoelectric effect demonstrate the particle nature of light?

The photoelectric effect shows that light can behave like a particle, as the energy of the ejected electrons is dependent on the frequency (or color) of the light rather than its intensity. This is explained by the concept of photons, which are discrete packets of energy that make up light.

3. What is the significance of the photoelectric effect in modern technology?

The photoelectric effect has many practical applications, such as in solar panels, photodiodes, and digital cameras. It also played a crucial role in the development of quantum mechanics, which has greatly advanced our understanding of the behavior of matter and energy at a microscopic level.

4. What factors affect the photoelectric effect?

The photoelectric effect is influenced by the intensity and frequency of the incident light, as well as the properties of the material being exposed to the light. Higher intensity light and higher frequency (shorter wavelength) light tend to result in a higher number of ejected electrons.

5. How does the photoelectric effect support the wave-particle duality theory?

The photoelectric effect is an important demonstration of the wave-particle duality theory in that it shows that light can exhibit both wave-like and particle-like behaviors. It also helped to reconcile the conflicting theories of light at the time, as it showed that light could act as both a wave and a stream of particles depending on the situation.

Similar threads

Replies
1
Views
833
Replies
5
Views
578
Replies
1
Views
1K
  • Introductory Physics Homework Help
2
Replies
35
Views
1K
Replies
1
Views
3K
  • Quantum Physics
Replies
12
Views
667
  • Quantum Physics
Replies
10
Views
2K
  • Electromagnetism
Replies
4
Views
10K
  • Electromagnetism
Replies
6
Views
14K
Back
Top