Em Waves Question 71
Question: Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell. The work function of the cathode surface is 4.2 eV. In order to reduce the photo- current to zero the voltage of the anode relative to the cathode must be made
Options:
A) -4.2V
B) -9.4V
C) -17.8V
D) +9.4 V
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ E=W _{0}+eV _{0} $ For hydrogen atom, $ E=+13.6eV $
$ \
Therefore +13.6=4.2+eV _{0} $
$ \Rightarrow V _{0}=\frac{(13.6-4.2)eV}{e}=9.4V $ Potential at anode $ =-9.4V $
BETA
