Experimental Measurement of Planck’s Constant

Experimental Measurement of Planck’s Constant

• Apparatus:
  • Light source with known wavelength
  • Photoelectric cell
  • Variable voltage power supply
  • Ammeter and voltmeter
• Procedure:
  • Illuminate the photoelectric cell with light of a known wavelength.
  • Adjust the voltage to stop the emitted photoelectrons (stopping potential).
  • Measure the stopping potential using the voltmeter.
  • Repeat the experiment with different wavelengths of light.
• Calculations:
  • Use the equation $eV=hf-\varphi$, where $e$ is the electron charge, $V$ is the stopping potential, $f$ is the frequency of the light, and $\varphi$ is the work function of the material.
  • Plot stopping potential $V$ against frequency $f$ and determine the slope, which is he\frac{h}{e}eh​.
• Error Minimization:
  • Use monochromatic light sources with precise wavelengths.
  • Calibrate the voltage measurement equipment accurately.
  • Perform the experiment in a dark environment to avoid interference from ambient light.