In regards to the photoelectric effect, why does an increase in brightness of a colored light eject more electrons from a metal sheet?
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Brightness and Photoelectric effect
- Thread starter SaintJude
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Brightness is the subjective interpretation of intensity of light. Higher intensity, more photons, more ejected ions
Ah I see. Thank I think, with help from all the SDNers, I finally understand the key concepts behind photoelectric effect. Wrote them up for my own reference and anyone who may still be shaky a bit.
1. The energy of photon increases with rising frequency. And we mostly discuss electrons being ejected from metals b/c they are "weaklings" w/ low electronegatives & don't hold on to valence electrons well.
So metals of higher ionization energies, will have a higher threshold frequency & (higher work function), right? B/c the work function just dictates how much energy is required to eject an electron from the metal.
2. When the frequency of an incoming photon (same as frequency of the light) is AT the threshold function of the metal, electrons WILL escape from the metal, albeit just barely.
3. The famous equation K = hf-W. All the equation is really telling you is any additional left over energy can be used to get those ejected electrons moving! So the excess energy = kinetic energy at which the ejected electrons will move.
4. Intensity (Brightness--thanks loveroforganic!). Intensity is related to the number of photons. I think i'm gonna view each photon as a tiny lightbulb and the brighter the light is the more lightbulbs there are. So increasing intensity will increase the no. of ejected electrons, b/c each photon will transmit the energy to the metal to eject an electron. But b/c photons are "pre-packaged balls of energy" so to speak, the energy cannot be also used to increase the speed of the ejected electrons.
Milksi said it best: "The photoelectric effect is an interaction between a single proton and electron. If you add more photons, the interaction does not change but you have more electrons being excited"
5.Frequency of light. Frequency of light (change in color for visible light) can increase KE. B/c the hf term will increase in the equation KE = hf-W, imparting more speed to the electrons.
Yay, took me long time, but I hope everything is correct.
1. The energy of photon increases with rising frequency. And we mostly discuss electrons being ejected from metals b/c they are "weaklings" w/ low electronegatives & don't hold on to valence electrons well.
So metals of higher ionization energies, will have a higher threshold frequency & (higher work function), right? B/c the work function just dictates how much energy is required to eject an electron from the metal.
2. When the frequency of an incoming photon (same as frequency of the light) is AT the threshold function of the metal, electrons WILL escape from the metal, albeit just barely.
3. The famous equation K = hf-W. All the equation is really telling you is any additional left over energy can be used to get those ejected electrons moving! So the excess energy = kinetic energy at which the ejected electrons will move.
4. Intensity (Brightness--thanks loveroforganic!). Intensity is related to the number of photons. I think i'm gonna view each photon as a tiny lightbulb and the brighter the light is the more lightbulbs there are. So increasing intensity will increase the no. of ejected electrons, b/c each photon will transmit the energy to the metal to eject an electron. But b/c photons are "pre-packaged balls of energy" so to speak, the energy cannot be also used to increase the speed of the ejected electrons.
Milksi said it best: "The photoelectric effect is an interaction between a single proton and electron. If you add more photons, the interaction does not change but you have more electrons being excited"
5.Frequency of light. Frequency of light (change in color for visible light) can increase KE. B/c the hf term will increase in the equation KE = hf-W, imparting more speed to the electrons.
Yay, took me long time, but I hope everything is correct.
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b/c they are "weaklings" w/ low electronegatives
I'm rusty on this stuff, but I don't remember if electronegativity is related (at all, directly, etc) to the photoelectric effect. Have someone confirm this, and make sure you use the terms carefully. You used ionization energy right after that statement, and that's more what I remember
Everything else looks good to me
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Shouldn't the increase in intensity of the photons only effect the number of electrons emitted as long as they are above the threshold frequency of the photoelectric material?
Say you have a material with a certain energy threshold upon which it will emit an electron with incident light. You can have a massive intensity of light but if the frequency is below the threshold frequency you still get no emitted electrons. The number of collisions of photons with photoelectric material that will produce a current will only vary once your incident light has enough energy (frequency high enough, E=hf)
Say you have a material with a certain energy threshold upon which it will emit an electron with incident light. You can have a massive intensity of light but if the frequency is below the threshold frequency you still get no emitted electrons. The number of collisions of photons with photoelectric material that will produce a current will only vary once your incident light has enough energy (frequency high enough, E=hf)
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That's correct, was the opposite said somewhere?
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