The work function of a material refers to the minimum energy required to remove
ID: 883901 • Letter: T
Question
The work function of a material refers to the minimum energy required to remove an electron from the material. Assume that the work function of gold is 4.90 eV and that of cesium is 1.9 eV. Calculate the maximum wavelength of light for the photoelectric emission of electrons for gold and cesium.
Take the value of the wavelength calculated for gold. If the light of this wavelength is used, calculate the kinetic energy Ek of an escaping electron for:
a. Gold.
b. Cesium.
Present your energy both in J and eV.
Explanation / Answer
E = hf
= h nu / lamda
lamda = h nu / E = 1240eV / E (in eV)
for gold work funtion is = 4.90 eV
ther fore work funtion wave length is = 1240 / 4.9 = 253.06 nm
ther fore work funtion wave length is = 1240 / 1.6 = 775 nm
E = work funtion + K.E
the energy used for gold is = 4.90 eV, so it just knock out the electron , no Ke is obtained for gold electron
4.9 = 4.9 + KE ===> KE = 4.9 -4.9 = 0 eV
the energy used for Cesium is = 4.9eV,
4.9 = 1.6 + KE ===> KE = 3.3eV
= 3.3eV X 1.6 10-19J/eV = 5.28 X 10-19 J
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