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32 votes
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Why does classical physics imply every mode of vibration should have the same thermal energy?

This classical prediction comes from the equipartition theorem of statistical mechanics, though I have some issues with exactly how the statement you quote is worded. The equipartition theorem is for ...
rob's user avatar
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30 votes
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How can a photon collide with an electron?

This is an answer by a particle physicist that has been working with data for forty years: Photons and electrons are quantum mechanical entities, and to really really understand their interactions, ...
anna v's user avatar
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30 votes
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What is different in the morning sunlight so it doesn't produce as much electricity as at noon?

When the sun is near the horizon, the sun rays have to travel through more air to get to you than when it's directly overhead. This phenomenon is known as atmospheric extinction, and this page has a ...
Michael Seifert's user avatar
26 votes

Electron leaving the atom

For a photon to give rise to a real (not virtual) electron/positron pair it must possess an energy of slightly greater than one million electron volts. This is a very energetic photon indeed. In ...
niels nielsen's user avatar
24 votes
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Photoelectric effect, low frequency light

For simplicity let's consider the photoelectric effect in a thin metal foil: The first step in the photoelectric effect is when a photon strikes an electron in the metal and transfers all its energy ...
John Rennie's user avatar
23 votes

How can a photon collide with an electron?

It depends what you mean by "size". Light spreads out like a ripple in water so once that ripple reaches some object floating in the water it will disturb the object. Does the ripple have some ...
Andrew's user avatar
  • 902
22 votes

Photoelectricity in daily life

The metals that are used in photoelectric experiments belong to the first group of the periodic table. They are often called Alkali metals. They have the highest electropositive nature in their ...
Mitchell's user avatar
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19 votes

Photoelectricity in daily life

Sometimes the effects do become visible in electronics. One example is the case where Raspberry Pi 2 could be crashed by camera flashlight: Upton explained that the semiconductor material used to ...
jpa's user avatar
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16 votes

Electron leaving the atom

The answer is, it does happen. Just at largely different energies. This picture (taken from this thesis, page 10) summarizes it quite nicely for scattering on Cu (Copper) atoms: Photoelectric ...
Cream's user avatar
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14 votes

Photoelectricity in daily life

They do, but it's too small to notice on a human scale. On the scale of electronics, you absolutely can see it. We have photoresistors and photodiodes which rely on this effect. You need to be ...
Graham's user avatar
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13 votes

Why doesn't photoelectric current increase with frequency of the incident wave?

In the context of the photoelectric effect, the key thing to remember is that you get one electron per photon. Current is a measure of how much charge flows per unit time, which is proportional in ...
Daksh Shah's user avatar
12 votes
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Is photoelectric effect a surface phenomenon?

It is somewhat matter of what precisely one would refer to as photoelectric effect. As far as the radiation-electron mechanism of transfer of energy, there is no direct role played by surface. ...
GiorgioP-DoomsdayClockIsAt-90's user avatar
12 votes

Electron leaving the atom

This is actually a good question. Because of conservation of momentum/energy, this cannot happen. A single photon will not decay into an electron-positron pair such that they would exist as two ...
joseph h's user avatar
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11 votes

Why does classical physics imply every mode of vibration should have the same thermal energy?

There is so called equipartition theorem in classical statistical physics that says that under some conditions all degrees of freedom have the same average energy if the temperature is fixed. The ...
akhmeteli's user avatar
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10 votes

Why did Albert Einstein receive a nobel prize?

What Einstein added to the discussion was the idea that electromagnetic energy comes in little particle-like packets. That was a very radical concept at the time (and frankly still is).
Terry Bollinger's user avatar
10 votes
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Cause behind photoelectric effect

A light ray has an oscillating electric field associated with it, and this oscillating electric field will make electrons oscillate when the light ray passes through them. Note that I'm talking about ...
John Rennie's user avatar
10 votes

How can a photon collide with an electron?

Both photons and electrons may be considered point-like particles, but the interaction/force that they feel has a range: the electromagnetic interaction has a pretty long range. Actually it is ...
Davide Dal Bosco's user avatar
10 votes

Why do silicon photodiodes respond to a wavelength range of 190-1100nm?

It's somebody's practical limit. There's usually some sort of thin "dead layer" on the diode surface. It's close to perfectly transparent at long wavelengths, but as you move into the UV, it ...
John Doty's user avatar
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9 votes

What's the difference between the work function and ionisation energy?

There is definitely a relationship between the work function and ionisation energy of the elements. See the above figure in which I plotted the work functions (blue) and ionisation energies (yellow) ...
Ben Harkema's user avatar
9 votes

Why is Maxwell's theory insufficient to explain the photoelectric effect?

Photoelectric effect can be observed instantaneously when light is flashed and it is independent of intensity of the light. If wave model were at play here, intensity of the light (amplitude of the ...
user3394040's user avatar
9 votes

Photoelectric effect as proof of the particle-like nature of photons

The energy is delivered to the metal in discrete packets. If you think of light as a wave, than one may expect that a low-energy colour of light should be able to (eventually) liberate electrons ...
Bob's user avatar
  • 1,709
9 votes

Basics of photoelectric effect

MAIN QUESTION: Why doesn't the frequency affect the photocurrent? It does affect it, in general. It just does not affect the number of ejected photoelectrons (to zeroth order). If you google for the ...
hft's user avatar
  • 20.7k
8 votes

Electron leaving the atom

In order to create an electron positron pair, a photon needs to have at least the energy of the mass of the two particles (511 keV * 2 = 1.02 MeV). The photons involved in the photoelectric effect are ...
Señor O's user avatar
  • 7,668
8 votes

Basics of photoelectric effect

None of the above answers have addressed your point because your point, in fact, does not exist. I'll give you an analogy. Consider a highway where you have, in one part of it, a lower speed limit, ...
Alfred's user avatar
  • 4,236
8 votes

Why electrons do not emit electromagnetic radiation when they "jump" to an excited state?

According to electromagnetism, accelerating charges emit electromagnetic (EM) radiation. This is according to classical electromagnetism. In classical electrodynamics, sources can be point particles ...
hft's user avatar
  • 20.7k
7 votes
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Why doesn't saturation current in the photoelectric effect depend on the frequency of light absorbed by the metal emitter?

In the context of the photoelectric effect it is probably not a good idea to use the equation $ I = nAev$ because the speed of the electrons is not constant across the gap. It is better to use $I=Ne$ ...
Farcher's user avatar
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7 votes

Photoelectric effect, low frequency light

If you leave light shining onto that metal, for long enough, does the energy of the individual photons accumulate, on the electrons, so eventually they will ionize, or does this not happen? What am I ...
anna v's user avatar
  • 234k
7 votes
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Photoelectric effect confusion

The photoelectric effect expresses the fact that light behaves both as a wave and a particle. The fact that you use frequency to calculate the energy is obvious enough to you already that its wavelike ...
Andrew's user avatar
  • 902
7 votes

How can a photon collide with an electron?

Great question! You are correct in that an electron doesn't have a 'size' in the sense that it's not actually a little billiard ball sitting out in space. For that matter, neither is a photon. In ...
taciteloquence's user avatar

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