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electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 A . Calculate thrshold frequency `(v_(0))` and work funcation `(W_(0))` of the metal.

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i. `lambda=6800 Å=6800xx10^(-10) m`
`E=(hc)/lambda=(6.63xx10^(-34)xx3xx10^(8))/(6800xx10^(-10))J`
`=(6.63xx3)/(68)xx(10^(-8))/(1.6xx10^(-19))eV=1.83 eV`
`v_(0)=W/h=(1.83xx1.6xx10^(-19))/(66xx10^(-34))=4.41xx10^(14) s^(-1)`
ii. `W_(0)=hv_(0)=6.63xx10^(-34)xx4.41xx10^(14)`
`=2.91xx10^(-19)J`
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