Planck's "quantum of action" and extern photoelectric effec effect (line separation by a diffraction grating)

Principle

The photoelectric effect is one key experiment in the development of modern physics. White light from a filament lamp is filtered by a grating spectrometer and illuminates a photocell. The maximum energy of the ejected electrons depends only on the frequency of the incident light, and is independent of its intensity. This law appears to be in contradiction with the electromagnetic wave theory of the light, but it becomes understandable in the frame of the corpuscular theory of light. The stopping voltage U₀ at different light frequencies is determined by the I /U characteristicsof the photocell and plotted over the corresponding light frequency f .Plancks quantum of action is then determined from this graph.

Tasks

1. Calculate the light frequency f  in dependence on the spectrometer angle
2. Experimentally determine the stopping voltage U₀ for different light frequencies and plot it over light frequency f
3. Calculate Plancks constant from the dependence of the stopping voltage U₀ on the light frequency f

What you can learn about

• Photon energy
• photon absorption
• external photo effect
• work function
• photocell
• quantum theory
• Plancks constant
• grating spectrometer

Literature for this article als follows

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