Infrared:

The longest IR waves are around 1 mm in length; the reddest visible light has a wavelength of a slight less than 0.001 mm. This is a period of a thousand fold, or three mathematical orders of magnitude. In terms of the frequency, IR spectrum lies beneath the visible red spectrum, and it is from this fact which it acquires its name (i.e., infra- means "below"). Our bodies logic IR radiation as warmth or heat. The IR rays are not exactly heat, though they generate heat whenever they strike an absorptive object like the human body.

The Sun is a bright source of IR; it discharges just about as much IR as visible light. The other sources of IR involve luminous light bulbs, fire, and electrical heating elements. When you have an electric stove and switch on one of the burners to low, you can sense the IR radiation from it even however the element emerges black to the eye.

The infrared radiation can be identified by special films which can be used in most common cameras. Several high-end photographic cameras have focus numbers for IR and also for visible light printed on their lens controls. The Glass transmits IR at the shorter wavelengths (close to IR) though blocks IR at the longer wavelengths (distant IR). Whenever you take an IR photograph in visible-light darkness, warm objects illustrate up clearly. This is the theory by which few night-vision apparatus works. The Infrared-detecting equipment has been used lately in wartime to sense the presence and movement of personnel.

The fact that glass transmits close to IR though blocks far IR is responsible for the ability of glass greenhouses to keep interior temperatures much higher than that of the exterior environment. It is also responsible for the tremendous heating of automobile interiors on sunny days whenever the windows are closed. This effect can be used to benefit in energy-efficient homes and office buildings. The large windows with southern exposures can be prepared with blinds which are opened on sunny winter days and closed in cloudy weather and at night.

The IR radiation at low and reasonable levels is not dangerous and however has been used therapeutically to aid relieve the anxiety of muscle strains and joint injuries. At high intensity, though, IR radiation can cause burns. In huge structural or forest fires, such radiation can burn the clothing off a person and then exactly cook the body alive. The most tremendous earthly IR radiation is generated by the detonation of a nuclear bomb or by an asteroid shock. The IR burst from a 20-megaton weapon (equal to 2 x 10⁷ tons of conventional explosive) can kill every uncovered living organism within a radius of some kilometers.

In some parts of the IR spectrum, the environment of our planet is opaque. In close to the IR among around 770 nm (i.e., the visible red) and 2,000 nm, our environment is logically clear. The water vapor causes reduction in the IR among the wavelengths of around 4,500 and 8,000 nm. Carbon dioxide (CO₂) gases interfere with the transmission of IR at wave-lengths range from around 14,000 to 16,000 nm. The snow, Rain, fog, & dust interfere with the propagation of IR. The presence of CO₂ in the environment remains the surface warmer than it would be when there were less CO₂. Most of scientists agree that rising CO₂ in the atmosphere will generate an important rise in the average surface temperature. This greenhouse effect obtains its name from the fact that the CO₂ in the Earth's environment treats IR in much similar way as the glass in a greenhouse.