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Determining Planck's Constant [Resolved]

  • Thread starter Hapablap
  • Start date
  • #1
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*Edit: Nevermind, I realize where I went wrong!

Homework Statement


The following graph shows the kinetic energy of the most energetic photoelectrons as a function of the frequency of light falling on the cathode in a photoelectric cell.

http://img208.imageshack.us/img208/3421/fwby.jpg [Broken]

Use the graph to determine the value of Planck's constant.

Homework Equations


E = hf
h = E/f

The Attempt at a Solution


I'll choose the point where E = 3.0 eV and f = 10.0 Hz for my calculation.

First I'll convert eV to Joules:
3.0 eV x (1.60 x 10^-19 J / 1 eV) = 4.8 x 10^-19 J

Now the calculation:
h = E/f
h = (4.8 x 10^-19 J) / (10.0 x 10^14 Hz)
h = 4.8 x 10^-34 J(s)

We already know that the value of Planck's constant is 6.63 x 10^-34 J(s), so my answer is off.

Any suggestions?
 
Last edited by a moderator:

Answers and Replies

  • #2
11,685
5,254
looks like you need the slope of the line but what you calculated was the slope of the line going thru 0,0
 

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