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Salvador
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When a fixed intensity and frequency Em radiation strike a metal plate , is the outgoing electron/s with a higher energy if the plate is charged to some potential (volts) than if the plate is simply neutral?
Drakkith said:The intensity and frequency don't matter (not much at least, as long as the frequency is high enough to eject an electron). A single photon will eject a single electron, whose energy is the energy of the photon plus any extra energy from the charged plate, minus the work function (the energy needed to remove the electron from the metal).
sophiecentaur said:The frequency of the photons will affect the speed (kinetic energy) of the ejected electrons and that can be determined by measuring the so-called Stopping Potential (look it up) of the photoelectrons. The graphs in this link show how any energy beyond the threshold (work function) of the metal goes into the KE of the emitted photo electron. It is always worth while noting that the graph shows the Maximum energy. There will be electrons with lower energies, too (You could imagine some of them having been 'buried' a small distance below the surface, although this a slightly naive model)
How much have you read about this topic, apart from what we have been telling you? There are hundreds of Google hits and there has to be one which will be at a level appropriate to your present knowledge. Simple Q and A is not always the best way to acquire knowledge.
Salvador said:if I charged the vacuum separated plates to say 10kv, and then used a very low intensity but high frequency laser on the positive plate , would the current between the plates would be proportional to the intensity of the incoming photons ?
OK ... to answer your question: yes, the current will be proportional to the laser intensity, as long as the intensity is not too high; if too high you will initiate non-linear effects, such as multi-photon absorption, or melting/vaporization of the target.
Salvador said:but if the laser radiation causes the photoelectron emission and forms a small current , shouldn't the current get bigger because the plates have a PD across them and now because of the photoelectron current the charges on the plates have a path through whioch they can discharge, so shouldn't the current then be the photoelectric current + whatever current the power supply of the plates can generate ?
Salvador said:Ok so if I have 10kv across the plates and a power supply capable of 10kv 1amp then how big of a current will flow between the plates if I switch on the laser and have the power supply already switched on to the plates?
Salvador said:I understand that the voltage is not the cause for electron flow in the photoelectric effect , I was rather thinking that once the photoelectrons form the current all the other electrons now can use that current to get to the other plate what they would normally want to do but seems like this is not the case.
Chronos said:There is a phenomenon known as field electron emission where the vacuum falls short of its billing as an ideal insulator.
Salvador said:well vacuum is the best insulator , then how about other mediums? air , or some semiconducor material , would then a current form from the plates which would be more than just the photo emitted electrons?
In other words could the current between two charged plates be the current of the emitted photoelectrons + that of the charge on the plates themselves if it would be in a medium that has some free charge carriers like electrons or holes like in a semiconductor material?
Salvador said:forgive me for that I wasn't clear enough, I was thinking about a semiconducting material , like in a mosfet when you apply an electrical field to the region between the source and drain via the gate you get a concentration of electrons which then conduct whatever current is run through the device from S to D.
If you leave out the Gate and just have a semiconducting layer and two metal layers at each side could photoemitted electrons too form a free electron current stream?
The photoelectric effect is the phenomenon where electrons are emitted from a material when it is exposed to light of a certain frequency or higher.
The energy of the incident light directly affects the maximum kinetic energy of the emitted electrons. If the energy of the incident light is below the material's work function, no electrons will be emitted.
The work function is the minimum amount of energy needed for an electron to escape from the surface of a material. It is a characteristic of the material and determines the threshold frequency for the photoelectric effect to occur.
The intensity of the incident light does not affect the maximum kinetic energy of the emitted electrons. However, it does affect the number of electrons emitted per unit time. Higher intensity light results in more electrons being emitted.
The Einstein's photoelectric equation, E = hf - Φ, relates the energy of the incident light (E) to the frequency of the light (f) and the work function of the material (Φ). It is used to calculate the maximum kinetic energy of the emitted electrons and to understand the relationship between the energy and frequency of light in the photoelectric effect.