Light Intensity
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Light Intensity
Hi guys, I was a bit confused as to how intensity does not affect the ejection of electrons. In other words, why does a higher intensity not eject an electron?
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Re: Light Intensity
Hey!
A higher intensity of light does increase the rate at which electrons are ejected. I think it was the frequency of light that does not change the ejection rate.
A higher intensity of light does increase the rate at which electrons are ejected. I think it was the frequency of light that does not change the ejection rate.
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Re: Light Intensity
The intensity of light won't affect the ejection of electrons, what will change the ejection of electrons is the wavelength.
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Re: Light Intensity
Just like they said above, wavelength will affect the ejection of electrons. As the wavelength decreases for a given metal, then the speed of the emitted electrons increases.
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Re: Light Intensity
~If light had only wave properties, then intensity should eject electrons, but it doesn't it has both particle (photons) and wave properties.
~You have to change the frequency (which increases the energy of the wave) instead of the intensity in order to eject the electron.
~Each photon must have enough energy to eject 1 electron
~In the photoelectric experiment, light sources with long wavelength (low frequency) couldn't eject electrons (even with high intensity light). Light is not acting like a classical wave (intense and bigger wave has more energy)
~Where as light sources with short wavelengths (High frequency), can eject electrons (even with low intensity light)
~You have to change the frequency (which increases the energy of the wave) instead of the intensity in order to eject the electron.
~Each photon must have enough energy to eject 1 electron
~In the photoelectric experiment, light sources with long wavelength (low frequency) couldn't eject electrons (even with high intensity light). Light is not acting like a classical wave (intense and bigger wave has more energy)
~Where as light sources with short wavelengths (High frequency), can eject electrons (even with low intensity light)
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Re: Light Intensity
If an electron is not ejected, turning up the intensity will not help it-- only shortening the wavelength will. However, if an electron is ejected, increasing the intensity will eject a higher number of electrons.
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Re: Light Intensity
A higher intensity won't eject electrons because light also has photon properties as shown by the photoelectric effect.
Re: Light Intensity
Another way to conceptualize "intensity" of light is that the brightness, or intensity, of light is directly related to the number of photons being emitted. But as everyone before me has said, in order for a beam of light to eject an electron from an atom, it must have exactly the right wavelength to bump the electron from its ground state to a higher level. As stated in lecture, 1 photon interacts with 1 electron, so it doesn't matter how many photons you have (the intensity of the light); it only matters what the frequency is. Increasing the frequency (shorter wavelength) of light was proven in the photoelectric experiment to allow electrons to be ejected even at low intensity. This experiment shows that light can act as packets of energy, meaning it has "particle-like" properties.
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Re: Light Intensity
Intensity of light is just the number of photons. So if each photon does not have enough energy on its own to eject an electron, it doesn't matter how many of them you shine at the metal surface, no electrons will be ejected. If each photon has enough energy on its own to eject an electron (high enough frequency) then increasing the intensity will increase the amount of ejected electrons.
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Re: Light Intensity
Hey,
So higher intensity waves do eject electrons if the frequency is high enough. However, if the light source has a low frequency, it won't eject electrons even with high intensity. This is because the energy of each photon (frequency) needs to be high enough for it to eject an electron. If the energy of the photon is high enough, then increasing the light intensity will result in more electrons ejected.
So higher intensity waves do eject electrons if the frequency is high enough. However, if the light source has a low frequency, it won't eject electrons even with high intensity. This is because the energy of each photon (frequency) needs to be high enough for it to eject an electron. If the energy of the photon is high enough, then increasing the light intensity will result in more electrons ejected.
Re: Light Intensity
The intensity of light is determined by the # of photons being ejected. Regardless of intensity, if the light doesn’t meet the condition of having a high frequency, electrons will not be ejected. Any intensity of light can eject electrons if the condition of high frequency is met.
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Re: Light Intensity
The light intensity only affects it the frequency of the photons is higher than the threshold energy. Then more light intensity would mean more photons, and because the energy of the photons is higher than the threshold energy, more electrons will be ejected. If the frequency is low, it won't matter how high the intensity (number of photons) is because it's one photon per electron interaction, there will be no ejected electrons.
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Re: Light Intensity
There is a certain threshold value of frequency that light must achieve for electrons to be ejected from a metal surface (this value is unique to every metal). If the threshold is not achieved, then electrons will not be ejected not matter how intense the light is. I am not sure if this explanation will help you understand better, but let us say you are shining visible light on a metal surface. You can continue to add more visible light, but you will not eject electrons. If you switch to using ultraviolet light, a light with a higher frequency than visible light, then electrons are immediately ejected.
Re: Light Intensity
Light intensity is defined by the number of photons being ejected. Electrons cannot be ejected unless the the light frequency is high enough. Therefore, electrons can be ejected at any intensity of light so long as the frequency is high enough.
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Re: Light Intensity
To eject an electron, each photon must have a certain energy. Increasing the intensity of light only increases the number of photons, not the energy of the photons, so electrons aren't ejected simply due to higher intensity light.
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Re: Light Intensity
Hi, intensity is the number of photons. Since electrons have particle like properties in addition to wavelike ones, they only accept certain wavelengths of light and therefore intensity doesn't affect if electrons are emitted.
Re: Light Intensity
Each photon interacts with one e-. If I understand it correctly then increasing the intensity of the light only increases the number of photons but the energy per photon has not increased so no individual photon can reach the threshold needed to begin ejecting electrons.
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Re: Light Intensity
Each photon interacts with an electron. Only when the photon has enough energy does it eject an electron. Increasing the intensity of light only increases the number of photons, not the energy that each photon has.
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Re: Light Intensity
Light has particle-like properties in addition to its wave-like properties, and according to the photoelectric effect, no matter how intense the light, if each photon doesn't have sufficient energy to overcome the threshold energy, an electron will not be ejected.
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Re: Light Intensity
If no electron is ejected, then increasing the intensity of the light won't make more electrons eject from the metal, only shortening the wavelength will do that. However, if there is an electron ejected from the metal initially, then increasing the intensity of the light will increase the electrons ejected from the metal.
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Re: Light Intensity
Intensity doesn't affect the ejection of electrons because the wavelength is what will affect it. :)
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Re: Light Intensity
Light intensity simply refers to the # of photons so increasing intensity would increase the number of photons but, if each individual photon has less energy than the work function (amount of energy required to eject electrons), then it doesn't matter how many photons you have since none of the photons have sufficient energy to even eject an electron.
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Re: Light Intensity
The reason that increasing intensity does not eject electrons is the wave particle duality of light. This means that light does not only exist as a particle, but also as a wave. While increasing intensity of light may not eject electrons, increasing the frequency by decreasing the wavelength would. This is because every individual photon must have enough energy to be ejected.
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Re: Light Intensity
To answer the question: merely increasing the intensity for a frequency of light that doesn't eject electrons will not help because there is not enough energy despite increasing the intensity. This is due to the idea that frequency is in a direct relationship with energy and if frequency and wavelength are in an inverse relationship then wavelength and energy are also inversely proportional. Therefore, as wavelength increases (a higher intensity) the energy decreases with the frequency still not allowing the electrons to be ejected. So, if you want to eject the electrons you must increase the frequency.
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Re: Light Intensity
Thinking of intensity as the number of photons basically quantifies the light emitted. One photon can only eject one electron, so that photon must have enough energy to eject a single electron on its own. If a single photon of the light already emitted does not have enough energy to do this, then adding more photons of the same energy won't either.
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