Question

  A sinusoidal electromagnetic wave of frequency 40.0 MHz travels in free space in the x direction, determine the wavelength and period of the wave.  

Answer 1

(a)

$$\lambda=\dfrac{c}{f},$$ $$\lambda=\dfrac{3\cdot10^8\ \dfrac{m}{s}}{4\cdot10^7\ s^{-1}}=7.5\ m.$$

(b)

$$T=\dfrac{1}{f},$$ $$T=\dfrac{1}{4\cdot10^7\ s^{-1}}=25\cdot10^{-9}\ s=25\ ns.$$