How Does the Photoelectric Effect Determine Planck's Constant?

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SUMMARY

The discussion focuses on determining Planck's constant using the photoelectric effect. An experiment measured the minimum potentials required to reduce photocurrent to zero for light frequencies of 8.5 x 1014 Hz and 2.35 x 1015 Hz, yielding values of 0.4V and 6.4V, respectively. The relationship between energy, frequency, and potential is established through the equation E = hf, where E represents energy, h is Planck's constant, and f is frequency. The key equation derived from the photoelectric effect is E = φ + Ek(max), linking the work function to the maximum kinetic energy of photoelectrons.

PREREQUISITES
  • Understanding of the photoelectric effect and its implications.
  • Familiarity with the equations E = hf and E = φ + Ek(max).
  • Basic knowledge of electric potential and photocurrent measurements.
  • Ability to manipulate equations involving energy, frequency, and potential.
NEXT STEPS
  • Calculate Planck's constant using the derived equations and experimental data.
  • Explore the implications of the photoelectric effect in modern physics.
  • Investigate the relationship between frequency and energy in quantum mechanics.
  • Review experimental setups for measuring the photoelectric effect.
USEFUL FOR

Students studying quantum mechanics, physics educators, and researchers interested in the fundamentals of the photoelectric effect and its applications in determining Planck's constant.

sofreshjay
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Homework Statement



In an experiment to determine the value of Planck's constant a negative potential was applied to the anode of a photoelectric cell and the minimum potential required to reduce the photocurrent to zero was mesure for incident light of various frequencies. For the frequencies of 8.5 x 10^14 Hz and 2.35 x 10^15 Hz the minimum potentials required were found to be 0.4V and 6.4V, respectively. Calculate Planck"s constant h.

Homework Equations



E=hf=hc/wavelength
E=mc^2

3. Attempt

I do not know how to start this. IN NEED OF DIRE HELP.
Thank you to anyone who helps.
 
Last edited:
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Even though I shouldn't reply since you didn't attempt anything, I will.

but you know that E=\phi +E_{k(max)} which is the same as hf=hf_0+\frac{1}{2}mv_{max}^2

When the photocurrent reaches zero, it means that the photoelectrons with max ke. just fail to reach the anode. So that the work done in stopping the electrons with max ke from reaching the anode=Loss in ke of the photoelectrons with max ke.

Can you express the last line in terms of an equation?
 

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