A photocathode has a work function of 2.4 eV.The photocathode is illuminated with monochromatic radiation whose photon energy is 3.5 eV.The wavelength of the illuminating radiation is closest to:
A)350 nm
B)330 nm
C)300 nm
D)380 nm
E)410 nm

Question

Quizplus · Accepted Answer

The correct answer is A because the wavelength of the illuminating radiation is closest to 350 nm. The work function of the photocathode is 2.4 eV, and the photon energy is 3.5 eV. The difference between the photon energy and the work function is the kinetic energy of the emitted photoelectrons. The kinetic energy of the photoelectrons is 3.5 eV - 2.4 eV = 1.1 eV. The wavelength of the illuminating radiation can be calculated using the following equation:λ = hc / Ewhere λ is the wavelength, h is Planck's constant, c is the speed of light, and E is the energy of the photon. Substituting the values into the equation, we get:λ = (6.626 x 10^-34 J s) x (3 x 10^8 m/s) / (1.1 eV x 1.602 x 10^-19 J/eV)λ = 350 nm

A Photocathode Has a Work Function of 2