Question

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength ` 6800` Å . Calculate threshold frequency `( v_0)` and work function `(W_0)` of the metal.

Answer 1

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`