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Question
Light from a hydrogen discharge tube is an incident on the cathode of a photoelectric cell. The work function of the cathode surface is 4.2eV. In order to reduce the photocurrent to zero, the voltage of the anode relative to the cathode must be made
Light from a hydrogen discharge tube is an incident on the cathode of a photoelectric cell. The work function of the cathode surface is 4.2eV. In order to reduce the photocurrent to zero, the voltage of the anode relative to the cathode must be made
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Solution
The correct option is D -9.4 V
Work function of cathode surface ϕ=4.2eV
Potential of cathode surface is −4.2 V
In order to reduce the photo current to zero. a lower potential must be applied to the anode surface having potential difference equal to 4.2 V.
Thus potential of anode relative to caathode Vanode=−4.2 V−4.2 V=−9.4 V
Work function of cathode surface ϕ=4.2eV
Potential of cathode surface is −4.2 V
In order to reduce the photo current to zero. a lower potential must be applied to the anode surface having potential difference equal to 4.2 V.
Thus potential of anode relative to caathode Vanode=−4.2 V−4.2 V=−9.4 V
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