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A monochromatic light source of power 5m...

A monochromatic light source of power 5mW emits `8 xx 10^(15)` photons per second. This light ejects photo electrons from a metal surface. The stopping potential for this set up is 2V. Calculate the work function of the metal.

Text Solution

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Given data `:` `P = 5 xx 10^(-3) W`,
`n = 8 xx 10^(15) ` photons per second
Energy of each photon,
`E = ( p)/( n ) = ( 5 xx 10^(-3))/( 8 xx 10^(15))`
`= 6.25 xx 10^(-19) J`
`= ( 6.25 xx 10^(-19))/( 1.6 xx 10^(-19)) eV`
`E = 3.9 eV`
Work function `, W_(0) = E - V_(0)`
`= ( 3.9 - 2 ) eV = 1.9 eV`
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