The electric field amplitude of an electromagnetic wave is $100 N C^{-1}$ and its frequency is 50 MHz. What is the magnitude of wave vector $(k)$. (given speed of electromagnetic wave is $3 \times 10^8 ms^{-1}$)

$\frac{\pi}{6}$ $\frac{\pi}{3}$ $\frac{6}{\pi}$ $\frac{3}{\pi}$

$\frac{\pi}{3}$

The correct answer is Option (2) → $\frac{\pi}{3}$