Electromagnetic Waves
Light is not a separate substance added to electromagnetism. It is a traveling electromagnetic field: electric and magnetic components oscillating together while energy moves through space.
How can fields keep traveling after leaving their original charges and currents behind?
A changing electric field is linked to magnetic change, and changing magnetic flux is linked to circulating electric field. In wave solutions, those coupled changes sustain a propagating disturbance.
Frequency and wavelength trade inversely while the wave speed in vacuum remains .
See the same electromagnetic wave as two perpendicular field components.
For an ideal plane wave in vacuum, the electric field, magnetic field, and propagation direction are mutually perpendicular.
Radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma radiation differ mainly in frequency and wavelength, not in their basic electromagnetic identity.
Mechanical waves need matter to oscillate. Electromagnetic waves are oscillations of the electromagnetic field itself and propagate through vacuum.
Now the four field laws form one dynamical theory.
Charge sources electric field. There are no observed magnetic monopoles. Changing magnetic flux curls electric field, while currents and changing electric flux curl magnetic field. Together, those relationships admit traveling electromagnetic waves.