Wave Mechanical Model of Electromagnetic Radiation:

In the wave mechanical model, the electromagnetic radiation is considered to be sinusoidal in nature that is, varying such a sine function. According to the Maxwell's theory, an electromagnetic wave can be visualized as oscillatory electric and magnetic fields travelling in the planes perpendicular to each other and also to the direction of propagation. This provides rise to its name that are electromagnetic radiation.

Therefore, since it is the electrical effect that is responsible for the phenomenon of interest to a chemist, it is generally represented in terms of the electric field only.

Figure: An EM radiation showing oscillatory electric and magnetic fields