2 Photoelectric effect 2 Light below a frequency of The fact that this plot was

Question

2 Photoelectric effect 2 Light below a frequency of The fact that this plot was not dependent upon the intensity of the incident light implied that the interaction was ike a particle which gave all its energy to the electrom anc jected it with that energy minus that which it took to escape the surface 439 x 1014 Hz or wavelength longer than 683 nm would not eject electrons 10 12 Frequency, Hz x10Data from Milian, 1916 Figure 1: Maximum kinetic energy of photoelectrons as a function of the frequency of light in the original experiment by Millikan in 1913 Consider the measurement of the maximum kinetic energy of the electrons extracted by photoelectric effect as a function of the frequency of impinging light in figure 1 Deduce the value of Planck's constant h . Calculate the work function of the metal used in the e xperiment, using the information in the figure The workfunction of nickel is 5.15 eV: compute the kinetic energy of electrons emitted by a chromium surface irradiated with ultra-violet light of wavelength equal to 180 nm.

Explanation / Answer

a)

Energy at frequency = 4.39 * 10^(14) Hz = 0 eV

Energy at frequency = 7.0 * 10^(14) Hz = 1 eV

1.6 * 10^(-19) = h(7-4.39) * 10^(14)

h = 6.1302 * 10^(-34)

b) Work Function = h * frequency

=> 6.1302 * 10^(-34) * 4.39 * 10^(14)

=> 2.6911 * 10^(-19) J

c) Kinetic Energy = Incident Energy - Work Function

Incident Energy = 1240/(lambda) eV = 1240/180 eV = 6.8888889 eV

Kinetic Energy = Incident Energy - Work Function

=> 6.8888889 eV - 5.15 eV

=> 1.73888889 eV

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