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.

Explanation

Threshold wavelength `(lambfa_(0))=6800 Å=6800xx10^(-10) m`
As `c=v lambda :. v_(0)=c/lambda_(0)=(3.0xx10^(8)" ms"^(-1))/(6800xx10^(-10) m)=4.41xx10^(14) s^(-1)`
Work function `(W_(0))=hv_(0)=(6.626xx10^(-34) J s)(4.41xx10^(14) s^(-1))=2.92xx10^(-19) J`