The work function for tungsten metal is 4.52eV a. What is the cutoff (threshold) wavelength for tungsten? b. What is the maximum

Question

1 month ago

12

The work function for tungsten metal is 4.52eV a. What is the cutoff (threshold) wavelength for tungsten? b. What is the maximum

kinetic energy of the electrons when radiation of wavelength 198nm is used? c. It is observed that the electrons may be prohibited from reaching the anode by applying a stopping potential. What is the stopping potential in the case when radiation of wavelength 198nm is used?

Physics

1 answer:

Maru [3.3K] · Answer 1 · 2026-04-01T16:37:39+03:00

a) 274.34 nm; b) 1.74 eV; c) 1.74 V. To tackle this problem, we must evaluate the energy balance concerning the photoelectric effect on tungsten: h*ν = Ek + W, with h standing for the Planck constant, Ek representing the kinetic energy of electrons, and W denoting the work function of the metal cathode. When determining the cutoff wavelength, we assume Ek = 0, which leads us to the conclusion that h*ν = W, resulting in (h*c)/λ = 4.52 eV. Thus, λ = (h*c)/4.52 eV, which calculates to λ = (1240 eV*nm)/(4.52 eV) = 274.34 nm. Following this, we can derive the kinetic energy for radiation at a wavelength of 198 nm, yielding (h*c)/λ - W = Ek; Ek = (1240 eV*nm)/(198 nm) - 4.52 eV = 1.74 eV. Finally, to halt these electrons, a stopping potential of 1.74 V must be applied, which will reduce the photocurrent to zero.