Question

The ejection of the photoelectron from the silver metal in the photoelectric effect exeriment can be stopped by applying the voltage of $0.35 V$ when the radiation $256.7 nm$ is used. Calculate the work function for silver metal.
A. $4.45 eV$
B. $7.86 eV$
C. $5.36 eV$
D. $6.78 eV$

Answer 1

Correct Answer - A
According to the phoeoelectric effect equation,
$hv = hv(0) +KE("max")$
$:. Hv(0) (work function) = hv - KE("max")$
Find the energy of photon $(hv)$ through wavelength:
$hv = (hc)/(lambda) =((6.6 xx10^(-34)Js)(3.0xx10^(8)ms^(-1)))/(256.7xx10^(-9)m)$
$= 0.077xx10^(-17)J = 7.7 xx 10^(-19) J$
$= (7.7xx10^(-19)J) ((1eV)/(1.6xx10^(-19)J))$
$= 4.8 eV$
Find the maximum kinetic enegry through stopping potential:
$KE(max) = eV(0) = 0.35eV$
$:.$ Work function $= (4.8eV) - (0.35eV)$
$= 4.45 eV$