Photoelectric Effect Lab

Photoelectric Effect Lab - Photoelectric Effect Lab...

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Photoelectric Effect Lab Introduction: Three fundamental questions of physics are: 1) What is matter? 2) What is energy? 3) What is the nature of the interaction between energy and matter? These questions are every bit as important today as they were at the turn of the 1900’s. In order to shed light upon the answers to these questions, Physicists have performed numerous experiments over the past 100 years. The results of these experiments have caused us to change our view of the world and form the basis for many subfields of engineering and science. In particular, the study of light energy has led to compact disks, laser surgery, optical detectors and communication, laser chemistry, checkout registers at Wal-Mart and many other important technologies. The high speed of light has also challenged our very notion of space and time. Although the prevailing theories appear to predict the answer to every experiment that has been tried, history tells us that the correct answer to these questions is probably still not known. Future experiments will probably demonstrate that our present theories are only approximations of the true answers to nature’s questions. One of the most important experiments from the early 20 th century was the photoelectric effect experiment. In this experiment, shinning a light upon a metal surface may cause electrons to be emitted from the metal. It is hard to believe that such a conceptually simple experiment could change the course of physics or lead to a Nobel Prize. However, Albert Einstein was awarded the Nobel Prize in Physics for his correct prediction of the results of this experiment in 1905 using a new model for the nature of light. Robert Millikan, co-founder of the California Institute of Technology and fellow Nobel Prize Winner, performed the careful experimental verification of Einstein’s predictions. Basic Experimental Concepts: An electron in a metal can be modeled as a being in an average potential energy well due to the net attraction and repulsion of protons and electrons. The minimum depth that an electron is located in the energy well is called the work function of the metal, Φ . Since different metal atoms have different number of protons, it is reasonable to assume that the work function depends on the metal. This is also supported by the fact that different metals have different values for electrical properties that should depend on the electron binding including conductivity. The electron in the potential energy well of a metal is shown below. It is analogous to a marble trapped in a water-well. The shallower the well
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This note was uploaded on 01/16/2012 for the course PHYS 4353 taught by Professor Dr.danielk.marble during the Fall '07 term at Tarleton.

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Photoelectric Effect Lab - Photoelectric Effect Lab...

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