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In a photo-electric cell, a retarding po...

In a photo-electric cell, a retarding potential of 0.5 V is required to block the movement of electrons from the cathode when monochromatic light of wavelength 400 nm is incident on its surface. Find the work function of the material of the cathode.

Text Solution

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Given : V=0.5 volt
So, stopping potential
`V_(0)=0.5` volt
`lamda=400` nm
W=?
We know,
`E_(n)=eV_(0)`
The photoelectric equation is
`hv=W+E_(n)`
`(hc)/(lamda)=W+eV_(0)`
`(6.6xx10^(-34)xx3xx10^(8))/(400xx10^(-9))=W+1.6xx10^(-19)xx0.5`
`W=4.95xx10^(-19)-8xx10^(-20)`
`=4.15xx10^(-19)J`
`W=2.59eV`.
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