Precision Photoelectric Effect

The Precision Photoelectric Effect uses three color filters to calculate Planck's Constant.

• Three Filters of Wavelength Included
• Students Use the Graph's Slope to Calculate Planck's Constant
• Apparatus Shows that Photoelectrons' Energy Relies on Wavelengths of Incoming Radiation

The Photoelectric Effect demonstrates that the energy of a photoelectron depends on the wavelength of the incoming radiation and not on its intensity. As monochromatic radiation irradiates the photocathode, a potential is applied opposing the energy of the emitted electrons. The voltage required to stop the current flow is proportional to the energy of the photoelectrons.

Plotting this voltage as a function of the reciprocal of the wavelength gives a straight line plot. Students can use the graph's slope to calculate Planck's Constant.

Ordering information: This kit includes three filters of wavelength: 470 nm, 580 nm, and 630 nm. A digital voltmeter or data-logging equipment to measure the stopping potential is required.