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Light from a hydrogen tube is incident o...

Light from a hydrogen 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

`-4.2 V`

B

`-9.4 V`

C

`-17.8 V`

D

`+9.4 V`

Text Solution

Verified by Experts

The correct Answer is:
B
`E = W_0 + eV_0`
for hydrogen atom , E = +13.6 eV
` therefore +13.6 = 4.2 + 2V_0`
`rArr V_0 = ((13.6 - 4.2) eV)/(e ) = 9.4 V`
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