lab41 - LAB#41 THE PHOTOELECTRIC EFFECT-PLANCK`S CONSTANT...

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LAB #41: THE PHOTOELECTRIC EFFECT-PLANCK`S CONSTANT INTRODUCTION: The experiment, which provided the first convincing experimental verification of the quantum theory, was suggested by Einstein in 1905. The actual phenomenon was observed by Hertz in 1887 and proved to be impossible to explain using the wave theory of light. Einstein postulated that not only is light emitted and absorbed in discrete but tiny bundles, as proposed by Max Planck, but it is propagated that way as well: flying through space like a hail of shot at the velocity of light. This conjecture nicely explained the photoelectric effect experimental results. In the experiment the velocity of the electrons leaving the surface of a metal, when irradiated by monochromatic light, depends upon the wavelength and not upon the intensity of the radiation. When Einstein made his suggestions, there was not sufficient quantitative evidence to confirm or deny his equations. Experimental work followed and subsequently the theory was completely verified. You will be able to repeat the essential part of the experiment that established the quantum theory of radiation. In the experiment, the photocathode is irradiated by a source of monochromatic radiation and a potential is applied to the tube so that it opposes the energy of the emitted photoelectrons. The voltage required to just stop the current flow is proportional to the energy of the photoelectron. Plotting the stopping potential as a function of the reciprocal of the wavelength of the radiation gives a straight line plot, the slope of which can be used to calculate Planck`s constant.
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lab41 - LAB#41 THE PHOTOELECTRIC EFFECT-PLANCK`S CONSTANT...

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