Quantum Physics

938 Chapter 28 Atomic PhysicsFigure P28.58. (a) If the photon emitted in theprocess is capable of ejecting a photoelectron fromtungsten (work function 4.58 eV), determine n f .(b) If a minimum stopping potential of V 0 7.51volts is required to prevent the photoelectron fromhitting the anode, determine the value of n i .ACTIVITIES1. With your partner not looking, use modeling clay tobuild one or more mounds on top of a table. Place apiece of cardboard over your mound(s), and assignyour partner the task of determining the size, shape,and number of mounds without looking. He is to dothis by rolling marbles at the unseen mounds andobserving how they emerge. This experiment modelsthe Rutherford scattering experiment.AnodePhotoelectron–+n fniTungsten2. Your instructor can probably lend you a small plasticdiffraction grating to enable you to examine thespectrum of different light sources. You can usethese gratings to examine a source by holding thegrating very close to your eye and noting the spectrumproduced by glancing out of the corner ofyour eye while looking at a light source. You shouldlook at light sources such as sodium vapor lights andmercury vapor lights used in many parking lots,neon lights used in many signs, black lights, ordinaryincandescent light bulbs, and so forth.V 0Figure P28.58