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Planck’s Constant by Photoelectric Effect Apparatus |
As it was observed in 1905, most metals under the influence of radiation, emit electrons. This phenomnon, defined as photoelectric emission, can now be observed and studied in detail, using this apparatus. Demonstrate to students that the emission process depends strongly on the frequency of radiation. The experiment will illustrate that for each metal a critical frequency exists such that light of a lower frequency is unable to liberate
electrons, while light of a higher frequency always does. The emission of electron occurs within a very short time interval after arrival of the radiation and the member of electrons is strictly proportional to the intensity of this radiation. Completing this experiment provides the strongest evidence that the electromagnetic field is quantified and the field consists of quanta of energy (photons), E= hn where n is the frequency of the radiation and h is the Planck’s constant.
This appratus includes a vacuum photo tube as the photo sensitive device and a halogen tungsten lamp (12V, 35W) as the light source. With the unit’s optical bench, the light source can be moved to adjust the distance between light source and phototube. Scale length is 400mm. A focus lens is fixed in the back end, and a drawtube is also provided to install the included color filters: 635nm, 570nm, 540nm, 500nm, and 460nm. Results are displayed on an easy-to-rad, seven-segment LED screen. Additionally, the apparatus features a regulated voltage power supply and high stability, low current digital nanoammeter. Output : ±15 V continuously variable. Accuracy : ±0.2%. 110V ±10%, 60Hz.
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