The work function ( $\Phi$ ) of some metals is listed below. The number of metals which will show…
The work function ( $\Phi$ ) of some metals is listed below. The number of metals which will show photoelectric effect when light of $300 \mathrm{~nm}$ wavelength falls on the metal is
Solution
Energy of photon $=\frac{h c}{\lambda} \mathrm{J}=\frac{h c}{e \lambda} \mathrm{eV}=\frac{6.625 \times 10^{-34} \times 3 \times 10^8}{300 \times 10^{-9} \times 1.602 \times 10^{-19}}=4.14 \mathrm{eV}$
For photoelectric effect to occur, energy of incident photons must be greater than work function of metal. Hence, only $\mathrm{Li}, \mathrm{Na}, \mathrm{K}$ and $\mathrm{Mg}$ have work functions less than $4.14 \mathrm{~V}$.
