Photoelectric effect and cutoff frequency

  • Thread starter lha08
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  • #1
lha08
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Homework Statement


I was just wondering that when I have a graph of the Stopping Potential versus Frequency of the light. How can I find the value for the cutoff frequency?
Wavelength Vo
160 nm 2.99 V
53 nm 19.18 V
80 nm 11.00 V
160 nm 2.93 V
187 nm 1.92 V

Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
Dadface
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What attempt have you made?
 
  • #3
rock.freak667
Homework Helper
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Write down the equation for the photoelectric effect and then use the fact that the stopping potential is the work done in stopping the electrons from having any kinetic energy.
 
  • #4
lha08
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What attempt have you made?

well i found the theoretical value of the slope: 4.14125 X 10^-15 Js/C and the actual value of the slope: 3.9512 X 10^15 J s/C but don't know how to use them to find the answer
 
  • #5
Dadface
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As rockfreak advised write down the equation.Next rearrange it to make V the subject of the equation and then compare what you have to the equation of a straight line.By comparison you should be able to identify what the gradient of the graph represent and what the intercepts on the y and the x axis represent.
 
Last edited:
  • #6
lha08
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As rockfreak advised write down the equation.Next rearrange it to make V the subject of the equation and then compare what you have to the equation of a straight line.By comparison you should be able to identify what the gradient of the graph represent and what the intercepts on the y and the x axis represent.

does the y intercept of the graph represent the work function?
 
  • #7
Dadface
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105
Did you plot V on the y axis?If so the intercept has the units of volts ie joules per coulomb.The work function has the units of Joules so what could the intercept represent?Also, look at the intercept on the x axis.
 

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