photons,Electrons Hw8

# photons,Electrons Hw8 - MasteringPhysics Assignment Print...

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[ Print View ] Physics 228 Spring 2008 Photons, Electrons, Matter Waves, and Atoms Due at 11:59pm on Monday, March 24, 2008 View Grading Details The Photoelectric Effect Experiment Learning Goal: To understand the experiment that led to the discovery of the photoelectric effect. In 1887, Heinrich Hertz investigated the phenomenon of light striking a metal surface, causing the ejection of electrons from the metal. The classical theory of electromagnetism predicted that the energy of the electrons ejected should have been proportional to the intensity of the light. However, Hertz observed that the energy of the electrons was independent of the intensity of the light. Furthermore, for low enough frequencies, no electrons were ejected, no matter how great the intensity of the light became. The following problem outlines the methods used to investigate this new finding in physics: the photoelectric effect . Suppose there is a potential difference between the metal that ejects the electrons and the detection device, such that the detector is at a lower potential than the metal. The electrons slow down as they go from higher to lower electric potential; since they must overcome this potential difference to reach the detector, this potential is known as the stopping potential . To reach the detector, the initial kinetic energy of an ejected electron must be greater than or equal to the amount of energy it will lose by moving through the potential difference. For the incident light to cause the ejection of an electron, the light must impart a certain amount of energy to the electron to overcome the forces that constrain it within the metal. The minimum amount of energy required to overcome these forces is called the work function . Different metals will have different values for . For an electron to reach the detector, the light must impart enough energy for the electron to overcome both the work function and the stopping potential. Part A If there is a potential difference between the metal and the detector, what is the minimum energy that an electron must have so that it will reach the detector? Express your answer in terms of and the magnitude of the charge on the electron, . Hint A.1 Relating potential difference to energy Hint not displayed ANSWER: = Part B Suppose that the light carries energy . What is the maximum stopping potential that can be applied while still allowing electrons to reach the detector? Part B.1 Find the energy of the ejected electron Page 1 of 8 MasteringPhysics: Assignment Print View 5/8/2008 http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1116519

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Express your answer in terms , , and . Part not displayed ANSWER: = Part C Classical electromagnetism predicted that should have increased as the intensity of the incident light increased.
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## This note was uploaded on 11/25/2010 for the course PHYSICS 228 taught by Professor Staff during the Spring '08 term at Rutgers.

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photons,Electrons Hw8 - MasteringPhysics Assignment Print...

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