Calculating Kinetic Energy of Photoelectrons in Ultraviolet Metal Interaction

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Homework Help Overview

The discussion revolves around calculating the kinetic energy of photoelectrons generated when ultraviolet light interacts with a metal. The specific scenario involves a metal with a work function of 3.0 eV and a wavelength of 200 nm, with an applied voltage of +1.0 V. Participants are exploring how this voltage influences the maximum kinetic energy of the emitted photoelectrons.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the formula for maximum kinetic energy (KEmax = hf - work function) and question the relevance of the applied voltage in the calculation of KEmax. There are inquiries about the relationship between the applied voltage and the stopping potential, as well as whether the applied voltage affects the energy required for electrons to be ejected from the metal.

Discussion Status

The discussion is ongoing, with participants expressing confusion about the role of the applied voltage and its implications for the stopping potential. Some participants are seeking clarification on whether the applied voltage can be equated to the stopping voltage, while others are attempting to understand the effects of the voltage on the ejection of electrons.

Contextual Notes

There is a mention of a stopping potential calculated to be approximately 6.211 V, which is significantly higher than the applied +1.0 V. This discrepancy raises questions about the assumptions being made regarding the applied voltage and its impact on the photoelectric effect.

JakeP
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< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color]

Hello guys, i need some help in clarifying a question.

A beam of ultraviolet light with wavelength of 200nm is incident on a metal whose work function is 3.0eV. Note that this metal is applied with +1.0V with respect to the ground, Determine the largest kinetic energy of the photoelectrons generated in this process.

Using the formula of KEmax = hf - work function, i can come up with an answer for it. However, from the question, it states the metal is applied with +1.0V with respect to the ground;Does this Voltage affect the KEmax? Because if i were to find stopping potential Vs using E=q|Vs|, Vs will result in approximately 6.211V, taking q to be 1.6 x 10^-19. So i believe that this voltage across the metal is redundant in the calculation.

Kindly advice.

Thank you guys!
 
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JakeP said:
Using the formula of KEmax = hf - work function, i can come up with an answer for it. However, from the question, it states the metal is applied with +1.0V with respect to the ground;Does this Voltage affect the KEmax? Because if i were to find stopping potential Vs using E=q|Vs|, Vs will result in approximately 6.211V, taking q to be 1.6 x 10^-19.
So if the applied potential was 6.211 V instead of 1 V, what would you answer for KEmax?
 
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Won't it be the same as KEmax?
 
I'm quite confused, is it alright to assume that the applied +1V on the metal is also the stopping voltage? And does this applied voltage on the metal makes it harder for the electrons to break the bond from metal -> Vacuum -> Being ejected ?
 
xTyler said:
I'm quite confused, is it alright to assume that the applied +1V on the metal is also the stopping voltage?
No. As said, the stopping potential is 6.211 V.

xTyler said:
And does this applied voltage on the metal makes it harder for the electrons to break the bond from metal -> Vacuum -> Being ejected ?
No. It changes what happens to the freed electron.
 
JakeP said:
Won't it be the same as KEmax?
What is the definition of the stopping potential?
 
I had this question figured out. Thanks!
 

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