The spectrum of electromagnetic waves stretches, in principle, over an
infinite range of wavelengths Different regions are known by different
names; g-rays, X-rays, ultraviolet rays, visible rays, infrared rays,
microwaves and radio waves in order of increasing wavelength  from 10–2 Å
or 10–12 m to 106 m They interact with matter via their electric and magnetic fields which set
in oscillation charges present in all matter The detailed interaction and
so the mechanism of absorption, scattering, etc