Type Wavelength
far infrared (IR-C) 100 - 15 μm
middle infrared (IR-B) 15 - 1.4 μm
near infrared (IR-A) 1.4 μm - 700 nm
solids infrared 35 - 15 μm
thermal infrared 30 - 3 μm
the Philips Infraphil 7529 was a heat lamp for therapeutic applications
Philips Infraphil 7529 heat lamp
The infrared part of the electromagnetic
spectrum can be divided into three
sub-bands, being near-, middle and far
infrared, also referred to as IR-A, IR-B
and IR-C. The wavelength of near
infrared ranges from 700 to 1400
nanometers while far infrared ranges from
15 to 100 micrometers. Far infrared is
capable of converting carbohydrates into
sugars and is does so in fruits as well as
in the human body. In fruit this conversion
accompanies the process of maturing.
Far infrared radiation only heats the
surface of organic materials while the
inside of the tissue is mainly heated by conduction. Middle- and, more specific, near
infrared penetrates deeper into the tissue causing a more equable heating and it is
this property that was used in heat lamps for therapeutic applications like the Philips
Infraphil 7529 heatlamp on display here.
There is no widely accepted standardisation of the wavelengths of the different types
of infrared radiation. The table listed below is therefore an indication only. Notice that
for the infrared spectrum different overlapping subdivisions exist.