Photoelectric Effect: Wave or Particle?

[brainyman89]

why does photoelectric effect show the corpuscular nature of light? can't we approach photoelectric effect phenomenon by regarding radiation as a wave? can't a wave just give the energy it carries to the electron causing it extracting?


another question: with respect to mechanical(classical) waves, is there any relation between the frequency and the energy that the wave carries similar to this relation E=h*f?

 

[mathman]

The main point of Einstein's paper was that if the wave length is too long, the effect won't happen no matter how intense the radiation is. However for shorter waves the effect will take place even for low intensity. His conclusion was that you need a photon model, not waves. to explain what is happening.

 

[zhermes]

why does photoelectric effect show the corpuscular nature of light? can't we approach photoelectric effect phenomenon by regarding radiation as a wave? can't a wave just give the energy it carries to the electron causing it extracting?

It isn't the photoelectric effect by itself that suggests the quantum nature of light---its the threshold at which the photoelectric effect begins (see the http://en.wikipedia.org/wiki/Work_function" ). An electron cannot be ejected by less than a single photon, below a given energy.

another question: with respect to mechanical(classical) waves, is there any relation between the frequency and the energy that the wave carries similar to this relation E=h*f?

Excellent question, and the answer is (perhaps surprisingly): no. Mechanical waves have an energy proportional to the square of their amplitude: E \propto A^2

 

[Drakkith]

Saying that a single "wave" of light only interacts with one electron is exactly like saying it is like a "particle" or "corpuscle". The problem is that in a classical wave, one wave of light wouldn't act with just one photon, hence saying it is a particle.

Honestly it helps to just think of matter having properties of BOTH waves and particles. Trying to describe it as a wave OR a particle at all times is confusing and pointlsess unless you are highly educated in the area.

 

[zhermes]

one wave of light wouldn't act with just one photon, hence saying it is a particle.

What?!

Honestly it helps to just think of matter having properties of BOTH waves and particles. Trying to describe it as a wave OR a particle at all times is confusing and pointlsess unless you are highly educated in the area.

Neither explanation will work at ``all'' times for anyone, regardless of their education.
In the case of the photoelectric effect, however, the particle viewpoint is much more instructive and important. In the end the distinction between wave and particle isn't clear-cut; this situation is one of the more black-and-white however.

 

[kloptok]

An important thing regarding the photoelectric effect that I keep reading is that classically, you can't explain how the increase of intensity doesn't increase the energy of the emitted electrons. The energy delivered by the wave is increased with intensity classically.

 

[Drakkith]

What?!

Whoops, had a brain fart there lol.

Meant to say: The problem is that in a classical wave, one wave of light wouldn't act with just one particle, hence saying that light is also particle and not just a wave.

 

[mathman]

Try reading "QED" by Feynman.