Light from a hydrogen discharge tube is incident on the cathode of a p – McqOptions

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1.	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
A.	-4.2V
B.	-9.4V
C.	-17.8V
D.	+9.4 V
Answer» C. -17.8V

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