$A$ mathematical representation of an electromagnetic wave is given by the two equations $E = E_{max} \cos(kx - \omega t)$ and $B = B_{max} \cos(kx - \omega t)$,where $E_{max}$ is the amplitude of the electric field and $B_{max}$ is the amplitude of the magnetic field. What is the intensity $I$ in terms of $E_{max}$ and universal constants $\mu_0, \epsilon_0$?

• A
  $I = \frac{1}{2} \sqrt{\frac{\mu_0}{\epsilon_0}} E_{max}^2$
• B
  $I = \frac{1}{2} \epsilon_0 c E_{max}^2$
• C
  $I = \frac{1}{2} \sqrt{\frac{\epsilon_0}{\mu_0}} E_{max}^2$
• D
  $I = \frac{1}{2} \sqrt{\frac{\mu_0}{\epsilon_0}} E_{max}$