Threshold Frequency: Equation & Electron Release

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Discussion Overview

The discussion revolves around the concept of threshold frequency in the context of the photoelectric effect, specifically focusing on the equation used to determine it and its relationship to the energy required to release an electron from a material. The scope includes theoretical aspects and mathematical reasoning related to the photoelectric effect.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant asks for the equation used to solve for the threshold frequency and questions whether it represents the minimum energy required to free an electron from the nucleus.
  • Another participant provides the equation W=hf_{0}, where W is the work function, h is Planck's constant, and f_{0} is the threshold frequency, affirming that the threshold frequency relates to the energy needed to release an electron.
  • It is noted that the energy of the photon is given by h*f, which should be sufficient to knock out the electron.
  • A clarification is made that the energy is just sufficient to bring an electron to the surface of the material, but not necessarily to eject it completely, depending on the interpretation of "knock out."
  • Another participant mentions the full equation E_{photon}=W+E_{K}_{max}, indicating that the equation for W as a function of threshold frequency is derived by setting the kinetic energy of the photoelectron to zero.

Areas of Agreement / Disagreement

Participants express varying interpretations of the threshold frequency and its implications for electron release, indicating that multiple competing views remain without a clear consensus on the nuances of the concept.

Contextual Notes

There are unresolved aspects regarding the interpretation of energy requirements for electron release and the conditions under which the threshold frequency applies, particularly in relation to kinetic energy considerations.

Gogsey
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What is the equation used to solve for the threshold frequency?

Is the threshold frequency the minimum amount of energy requird to free an electron from the nucleus?
 
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W=hf_{0}

where W is the work function, h is Planck's constant, and f_{0} is the threshold frequency. I believe the answer to your second question is yes.
 
We talk of threshold frequency because the energy of the photon is h*f. That energy should be sufficient enough to knock out the electron.
 
rgshankar76 said:
We talk of threshold frequency because the energy of the photon is h*f. That energy should be sufficient enough to knock out the electron.

To be precise this is just sufficient energy to bring an electron to the surface but not quite to knock it out of the metal. (Again this depends on how you interpret "knock out"). Thats why in the so called Einstein equation for photoelectric effect, there's a second term which accounts for the kinetic energy of the ejected photoelectron...if this term were zero, the electron would--in principle--stay there.
 
That is true. The full equation is

E_{photon}=W+E_{K}_{max}

As you can see, the equation for W as a function of threshold frequency is derived from this by setting the kinetic energy of the photoelectron to zero.
 
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