Photoelectric effect threshold

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Homework Help Overview

The discussion revolves around a problem related to the photoelectric effect, specifically determining the threshold wavelength of a surface based on stopping potentials observed with different wavelengths of light.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the relationship between stopping potential and photon energy, referencing Einstein's equation. There is an attempt to relate the stopping potentials observed with different wavelengths to find the threshold wavelength. Questions arise regarding the role of the surface thickness and the assumption of the work function.

Discussion Status

Some participants have attempted to solve the problem but express difficulty. Guidance is provided regarding the assumption of the work function and the relevance of the material thickness. Multiple interpretations of the problem are being explored, particularly concerning the assumptions made about the work function.

Contextual Notes

There is a mention of a missing work function value, and the thickness of the surface is noted but its significance is questioned. The problem context is framed within the constraints of a homework assignment.

Nairabhi
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When a cm thick surface is illuminated with light of wavelength lambda,the stopping potential is V. When the same surface is illuminated by light of wavelength 2lambda , the stopping potential is V/3.The threshold wavelength for the surface is ?

Homework Equations

The Attempt at a Solution

 
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Did you try to do this problem yourself?
 
Matterwave said:
Did you try to do this problem yourself?
Yes i tried but i am unable to solve it.
 
Nairabhi said:
Yes i tried but i am unable to solve it.

Hi Nairabhi. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

What equations do you have that you'll use here?
 
Last edited by a moderator:
NascentOxygen said:
Hi Nairabhi. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

What equations do you have that you'll use here?
See according to Einstein equation KE(Max)= Energy of photons - work function of surface, but since work function is not given i have assumed it
to be 0. And energy of photons is equal to hc/lamda and this energy is equal to KE(Max) or the stopping potential so using these equations and i am trying to find a relation between them and find the threshold wavelength .However i don't understand what role does the thickness of surface plays which is 1cm ?
 
Last edited by a moderator:
You should assume work function is non-zero, and is fixed at some value.

That material thickness may simply mean "of suitable thickness" for our purposes.

Does the textbook give the correct answer?
 

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