Speaker
Description
We present a comparative study of the photoelectric effect experiment aimed at enhancing conceptual understanding in undergraduate physics laboratories. A traditional mercury (Hg) lamp with optical filters is evaluated alongside a modified setup using multiple light-emitting diodes (LEDs) as discrete wavelength sources. In addition, two measurement approaches—stopping potential and direct potential methods—are implemented and compared.
The spectral characteristics of the Hg lamp-filter combination and the LEDs are analysed to assess their suitability as quasi-monochromatic light sources. Using a common photovoltaic cell setup, stopping potential is measured as a function of incident light frequency for both light sources, enabling the determination of Planck’s constant via linear regression. A direct potential measurement technique is also employed to provide an independent determination of the same quantity.
Results from both light sources and both measurement techniques will be used to show a consistent linear relationship between potential and frequency, yielding comparable values of Planck’s constant within experimental uncertainty. Differences in spectral width, intensity stability, and contact potentials are examined to explain observed deviations.
This comparative approach demonstrates that LEDs provide a viable and effective alternative to traditional Hg lamps, while the inclusion of multiple measurement techniques reinforces key quantum concepts and experimental reasoning. The experiment supports deeper student engagement by allowing cross-validation of results and critical evaluation of assumptions, making it well suited for modern physics education.
Keywords: Physics education, photoelectric effect, LEDs, mercury lamp, Planck’s constant, experimental comparison
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