Objective: Determine Planck’s constant using the decelerating voltage method
In a modified version of a classic set-up, light of known frequency passes through a ring-shaped anode to collide with a cathode, where it causes electrons to be released due to the photo-electric effect. The energy of the electrons can be determined by applying a decelerating voltage, which compensates for the flow of electrons towards the anode until no electrons are flowing. This demonstrates that the cut-off value of the decelerating voltage which corresponds to a current of zero is not dependent on the intensity of the light. The energy of the electrons is therefore similarly independent of intensity. By obtaining the cut-off voltages for light of varying frequency, it is possible to calculate Planck’s constant.
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