[tex]Dane:\\\lambda = 300 \ nm = 300\cdot10^{-9} \ m = 3\cdot10^{-7} \ m\\c = 3\cdot10^{8}\frac{m}{s}\\Szukane:\\f = ?\\\\\\\lambda = \frac{c}{f} \ \ \rightarrow \ \ f = \frac{c}{\lambda}\\\\f = \frac{3\cdot10^{8}\frac{m}{s}}{3\cdot10^{-7} \ m} = 1\cdot10^{8-(-7)}\cdot s^{-1}\\\\\boxed{f = 1\cdot10^{15} \ Hz = 1 \ PHz}[/tex]
