Worksheet 1b: Quantitative Photoelectric Effect - Modeling Physics
Worksheet 1b: Quantitative Photoelectric Effect - Modeling Physics
Worksheet 1b: Quantitative Photoelectric Effect - Modeling Physics
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NameDatePd<strong>Worksheet</strong> <strong>1b</strong>: <strong>Quantitative</strong> <strong>Photoelectric</strong> <strong>Effect</strong>Planck's Constant, h = 6.63 x 10 -34 J sec or 4.14 x 10 -15 eV secspeed of light, c = 3 x 10 8 m/selectron-volt, 1 eV = 1.60 x 10 -19 JExample:A metal with a work function of 4.5 eV is lit by incident light of frequency 3.5 x 10 15 Hz. Draw anenergy diagram and predict the maximum kinetic energy of the ejected electrons.Energy conservation for the photoelectric effect:work function + light energy = maximum electron kinetic energyE electric = work function = - 4.5 eVThe negative value means that energy must be transferred to the electron just to free it from the metal.E light = hf = (6.63 x 10 -34 J*s)(3.5 x 10 15 Hz) = 2.3 x 10 -18 J (1 eV / 1.60 x 10 -19 J) = 14.5 eVE kinetic = 14.5 eV - 4.5 eV = 10.0 eVProblems:1. Refer to the graph as you answer the followingquestions.a. What is the value and name of the slope ofthe line?b. What is the name and meaning of the x-intercept?ejectedelectronenergy(eV)0.0 eVincident lightfrequency (Hz)c. What is the name and meaning of the y-intercept?d. Describe the procedure used to collect the data for this graph.©<strong>Modeling</strong> Instruction Program 2008 1 L3-Photon Model ws <strong>1b</strong> v4.0
2. Light with a frequency of 7 x 10 14 Hz strikes three different metals. a) Draw an energy diagramfor each situation, b) determine which metals will eject electrons and c) find the maximum electronkinetic energy for each.a. Lithium work function = -2.3 eVb. Cesium work function = -1.90 eVc. Tungsten work function = -4.6 eV©<strong>Modeling</strong> Instruction Program 2008 2 L3-Photon Model ws <strong>1b</strong> v4.0
3. The lowest light frequency that will eject electrons from silver is 1.14 x 10 15 Hz. Complete anenergy diagram and find the work function of silver.4. The cutoff wavelength for calcium is 384 nm in a vacuum; at greater wavelengths no electrons areemitted. a) Find the work function for calcium. b) Find the maximum electron kinetic energycorresponding to incident light wavelengths of 260 nm and 450 nm. Appropriate energydiagrams should be part of your solution.©<strong>Modeling</strong> Instruction Program 2008 3 L3-Photon Model ws <strong>1b</strong> v4.0
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