[tex]dane:\\\lambda = 1000 \ m = 10^{3} \ m\\v = c = 3\cdot10^{8} \ \frac{m}{s}\\szukane:\\f = ?\\\\v = \frac{\lambda}{T}, \ \ ale \ \ T = \frac{1}{f}, \ zatem\\\\v = \lambda \cdot f \ \ /:\lambda\\\\f =\frac{v}{\lambda}\\\\f = \frac{3\cdot10^{8}\frac{m}{s}}{10^{3} \ m} = 3\cdot10^{5} \ Hz= 300 \ 000 \ Hz[/tex]
