and “far” infrared, since the physical
processes that produce these types of
radiation can be quite different. Near
infrared is that part of the spectrum
with wavelengths from 1 to 5
microns, just to the “red” side of
optical wavelengths. Far infrared is
that part of the spectrum that has
wavelengths of about 30 to 100
microns. 
 microwave (millimeter): The portion
of the electromagnetic spectrum with
wavelengths between 1 and 100
millimeters. Because these
wavelengths heat water molecules,
they are used in ovens to heat food.