Question

The work function of a particular substance is 5.3 × 10^-19 J. What is the photoelectric cutoff wavelength for this material? Enter your answer in nm.

Answer 1

Einstein described the photoelectric effect using a formula that relates the maximum kinetic energy (K_max) of the photoelectrons to the frequency of the absorbed photons (ƒ) and the threshold frequency (ƒ₀) of the photoemissive surface.

it can aslo be written as

where is work function

        is threshold frequency

   is Threshold wave length or cutoff wavelength

so from given data work function is 5.3 × 10^-19 J

cutoff wavelength is where h is Planck's constant 6.625*10^-34 Js, c is speed of light 3*10^8 m/s

substitutuing the values of h and c   = (6.626*10^-34 Js*3*10^8 m/s)/5.3*10^-19 J

we will get the cutoff wavelength as   = 375 nm