you have a photocathode and cannot remeber what target material you have. You do
ID: 1266156 • Letter: Y
Question
you have a photocathode and cannot remeber what target material you have. You do know that you have a light source with a wavelenght of 2.62x10^-7 meters.
a)based on the table below what material of materials could you not have?
b)for the possible materials your target is made of which one would emit electrons with the highest kinetic energy?
c)what would the kinetic energy of the emitted electrons be?
back up your answers with mathematical calculations.
element eV
Cs 2.14
Ca 2.87
Al 4.26
Ag 4.74
Be 4.98
W 5.22
Ni 5.35
Explanation / Answer
Energy of photon, E = h*c/lmada
= 6.634*10^-34*3*10^8/(2.62*10^-7)
= 7.6*10^-19 J
= 7.6*10^-19/(1.6*10^-19)
= 4.75 eV
a) so, we should not have Be,W,Ni
b) Cs. Beacuse it has less Work function.
c) KE = E - W
= 4.75 - 2.14
= 2.61 eV
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