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In the following arrangement y = 1.0 mm ...

In the following arrangement `y = 1.0 mm , d = 0.24 mm` and `D = 1.2 m`. The work function of the material of the emitter is `2.2 eV`. The stopping potential `V` needed to stop the photo current will be

A

`0.9V`

B

`0.5V`

C

`0.4V`

D

`0.1V`

Text Solution

Verified by Experts

The correct Answer is:
A
Fringe width `(beta) = (lamdaD)/d`
Here `beta = 2y implies 2y =(lamdaD)/d`
`lamda=(2yd)/D=(2xx1xx10^(-3)xx0.24 xx10^(-3))/(1.2)`
`=4 xx10^(-7)m=400Å`
`E(eV)=(12375)/(lamdaÅ)= (12375)/(4000) =3.1eV`
Now , `eV_0=E-phi_0`
`impliesV_0= (3.1- 2.2)/e eV=0.9V`
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