1.

A surface is irradiated with ultraviolet radiation of wavelength `0.2 mum`. If the maximum velocity of electron liberated from the surface is `8.8 xx 10^(5)m//s`, then find the work function of the surface.A. 3 eVB. 4 eVC. 5 eVD. 6 eV

Answer» Correct Answer - D
We know that E = hv = `(hc)/(lambda)`
`E=(6.6xx10^(-34)xx3xx10^(8))/(0.2 xx10^(-6))`
`=(1.98xx10^(-25))/(0.2 xx10^(-6))=9.9xx10^(-19)J`
Also, `" "E-W_(0)=(1)/(2)mv^(2)`
`9.9xx10^(-19)-W_(0)=(1)/(2)xx9.1xx10^(-31)(8.8xx10^(5))^(2)`
`W_(0)=9.9xx10^(-19)-3.52xx10^(-19)`
`W_(0)=6.38~~ 6 eV`


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