The electric and magnetic field of an electromagnetic wave is

Electromagnetic waves are those waves in which there are sinusoidal variation of electric and magnetic field vectors at right angles to each other as well as right angles to the direction of wave propagation.

The sinusoidal variation in both electric and magnetic field vectors $\overrightarrow{\mathrm{E}} \mathrm{and} \overrightarrow{\mathrm{B}}$ occurs, simultaneously. As a result, they attain the maxima and minima at the same place and at the same time. The amplitudes of the electric and magnetic field in free space are related by

$\frac{{\mathrm{E}}_0}{{\mathrm{B}}_0}=\mathrm{c}$

In figure, electric field vector $\left(\overrightarrow{\mathrm{E}}\right)$ and magnetic field vector $\left(\overrightarrow{\mathrm{B}}\right)$ are vibrating along Y and Z directions and propagation of electromagnetic wave is shown in X-direction.

Hence, electric and magnetic fields are in phase and perpendicular to each other.