In the photoelectric effect, what happens to the stopping voltage when the light frequency is decreased?
The energy of the emitted electrons is proportional to the energy of the incoming photon which is proportional to frequency.
Therefore if you decrease the frequency you decrease the energy of each electron and it takes less voltage to stop it.
See below excerpted from wikipedia:
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"Experimental results of the photoelectric emission
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" For a given metal of particular work function, increase in frequency of incident beam increases the maximum kinetic energy with which the photoelectrons are emitted, but the photoelectric current remains the same, though stoppage voltage increases.
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In the photoelectric effect, the stopping voltage refers to the minimum voltage that needs to be applied to stop the flow of electrons emitted from a material's surface when illuminated by light. When the light frequency is decreased:
1. Step: The energy of each photon of light is directly proportional to the frequency of the light, according to the equation E = hf, where E represents the energy of the photon, h is the Planck constant, and f is the frequency of the light.
2. Step: A decrease in light frequency corresponds to a decrease in the energy of each photon.
3. Step: The electrons in the material require a minimum amount of energy, known as the work function (ϕ), to be emitted from its surface. The work function is the minimum energy required to overcome the attraction between the electrons and the material.
4. Step: If the energy of each photon is lower than the work function of the material (E < ϕ), the electrons will not have enough energy to be emitted.
5. Step: As a result, the stopping voltage needs to be increased to a higher value to counterbalance the reduced energy of the photons and allow enough energy for the electrons to be emitted.
In summary, when the light frequency is decreased in the photoelectric effect, the stopping voltage must be increased in order to compensate for the decreased energy of the light photons and enable the emission of electrons.
In the photoelectric effect, the stopping voltage refers to the minimum voltage required to stop the flow of electrons emitted from a metal surface when light is incident on it. The stopping voltage depends on several factors, one of which is the frequency of the incident light.
To understand what happens to the stopping voltage when the light frequency is decreased, we need to consider the key principles of the photoelectric effect and the equations involved.
1. The photoelectric effect states that when light of sufficient frequency (typically ultraviolet or higher) falls on a metal surface, electrons are emitted from the surface.
2. The energy of the emitted electrons depends on the frequency (or wavelength) of the incident light. Higher frequency light carries more energy, which translates into higher kinetic energy for the emitted electrons.
3. The stopping voltage is the minimum potential difference applied across the electrodes that can stop the emitted electrons from reaching the positively charged electrode. It effectively counterbalances the kinetic energy of the emitted electrons.
Now, when the frequency of the incident light is decreased:
1. According to the equation E = hf, where E is the energy of a photon, h is Planck's constant, and f is the frequency of the light, the energy of each photon decreases. This means that the energy transferred to the emitted electrons will also decrease.
2. The maximum kinetic energy of the emitted electrons is given by the equation K.E.max = hf - W, where W is the work function of the metal (the minimum energy required to liberate an electron from the metal surface). As the frequency decreases, the energy of the photons decreases, resulting in a decrease in the maximum kinetic energy of the emitted electrons.
3. The stopping voltage is directly related to the maximum kinetic energy of the electrons. If the maximum kinetic energy decreases, the stopping voltage required to halt the electrons will also decrease.
Therefore, when the light frequency is decreased in the photoelectric effect, the stopping voltage required to stop the emitted electrons will also decrease.