Back, potentials 0.38V k 1.85V slop photo-currents due \'light\' frequencies (f)
ID: 1547392 • Letter: B
Question
Back, potentials 0.38V k 1.85V slop photo-currents due 'light' frequencies (f) '360 & 720' times 10^12 H_z respectively. Accepted electron charge magnitude 'c': 1.6 times 10^-C. Mass of an electron 'm': 9.1 times 10^-31 kg a] Based on the given photo-electric data determine 'h', Planck's constant b] Determine the work function (W) of the material constituting the photo-tube's cathode c] Determine the De Broglie wavelength of the photoelectrons stopped by the back potential 0.5V. Use result of part a. Do not use accepted 'h' value.Explanation / Answer
from Eienstein equation
hf = Wo + V*q
h*f1 = Wo + V1*e
h*f2 = Wo + V2*e
h*(f2-f1) = e*(v2-v1)
h*(720-360)*10^12 = 1.6*10^-19*(1.85-0.38)
plancks constant h = 6.53*10^-34 Js <<<-------answer
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(b)
Wo = hf1 - V1*e
Wo = (6.53*10^-34*360*10^12) - (0.38*1.6*10^-19)
work function Wo = 1.743*10^-19 J = 1.743*10^-19/(1.6*10^-19) = 1.09 eV
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(c)
kinetic energy of electron KE = V*q
Debrogile wavelength lambda = h/sqrt(2*KE*m)
lambda = 6.53*10^-34/sqrt(2*0.5*1.6*10^-19*9.1*10^-31)
lambda = 1.71*10^-9 m
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