✔ 最佳答案
As the name imples, electromagnetic waves have two components, an electric component and a magnetic component. The electric component is exhibited in the wave as time varying electric field, whereas the magnetic component is demonstrated as a time varying magnetic field.
Electromagnetic waves thus travel by the mutual interaction (i.e. mutual induction) of electric and magnetic fields.
Therefore, you could define 'electromagnetic waves' as waves that propagate by mutual interaction of their two basic components, time varying electric and magnetic fields.
Because the existence of both electric and magnetic fields do not need to medium, electromagnetic waves can travel through vacuum.
Light, by nature, is a form of elctromagnetic wave, with wavelengths between 400 nm (violet light) to 700 nm (red light).