Potassium and gold cathodes are used in a photoelectric-effect experiment. For e

Question

Potassium and gold cathodes are used in a photoelectric-effect experiment. For each cathode, find: The threshold frequency. The threshold wavelength. The maximum electron ejection speed if the light has a wavelength of 210 nm . The stopping potential if the wavelength is 210 nm . Throughout this problem, be sure to use 6.63×1034Js for Planck's constant.

A) The threshold frequency of potassium in hertz.

B) The threshold frequency of gold in hertz

C) The threshold wavelength of potassium in nanometers.

D) The threshold wavelength of gold in nanometers.

Explanation / Answer

(A) We know that work functiom of potassium is 2.3 eV
Work functtion = hvo
vo(threshold frequency) = 2.3*1.6*10-19 /(6.634*10-34) = 5.55*1014 Hz
(B) Similarly for gold work function is 5.1 eV
vo = 5.1*1.6*10-19 / (6.63*10-34) = 1.23*1015 Hz

(c) Threshold wavelength
   = cvo  = 3*108*5.55*1014 = 16.65*1022 m
(d) for gold
=  3*108*1.23*1015 = 3.69*1023 m

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