[tex]Dane:\\W = 1,8 \ eV = 1,8\cdot1,6\cdot10^{-19} \ J = 2,88\cdot10^{-19} \ J\\1 \ eV = 1,6\cdot10^{-19} \ J\\\lambda = 0,4 \ \mu m = 0,4\cdot10^{-6} \ m = 4\cdot10^{-7} \ m\\h = 6,63\cdot10^{-34} \ Js\\c = 3\cdot10^{8}\frac{m}{s}\\Szukane:\\E_{k} = ?\\\\Rozwiazanie\\\\E = W+E_{k}\\oraz\\E = h\cdot\frac{c}{\lambda}\\\\W + E_{k} =h\cdot\frac{c}{\lambda}\\\\E_{k} = h\cdot\frac{c}{\lambda}-W\\\\E_{k} = 6,63\cdot10^{-34} \ Js\cdot\frac{3\cdot10^{8}\frac{m}{s}}{4\cdot10^{-7} \ m}-2,88\cdot10^{-19} \ J[/tex]
[tex]E_{k} = 4,97\cdot10^{-19} \ J - 2,88\cdot10^{-19} \ J\\\\\boxed{E_{k} = 2,09\cdot10^{-19} \ J}[/tex]
