
Infrared (IR), sometimes called infrared light, is
electromagnetic radiation
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible ...
(EMR) with
wavelengths longer than those of
visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1
millimeter (300
GHz) to the nominal
red edge of the
visible spectrum, around 700
nanometer
330px, Different lengths as in respect to the molecular scale.
The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...
s (430
THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the
terahertz radiation range. Almost all
black-body radiation
Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spect ...
from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates
energy and
momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
, exerts
radiation pressure, and has properties corresponding to
both those of a
wave and of a
part