Energy of photon$=\frac{\text{h}\text{c}}{\text{λ}}\mathrm{\text{J}}=\frac{\text{h}\text{c}}{\text{e}\text{λ}}\mathrm{\text{e}}\mathrm{\text{V}}$

$=\frac{6.625\times {10}^{-34}\times 3\times {10}^8}{300\times {10}^{-9}\times 1.602\times {10}^{-19}}=4.14\mathrm{\text{e}}\mathrm{\text{V}}$

For photoelectric effect to occur, energy of incident photons, must be greater than work functions of metal. Hence, only Li, Na, K and Mg have work functions less than 4.14 V.