How does Infrared Work?

Infrared is electromagnetic energy. It is part of the electromagnetic spectrum which is comprised of radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays. In the electromagnetic spectrum, infrared falls in between microwaves and visible light waves. Its wavelengths are shorter than microwaves but longer than those of visible light.

The prefix infra derives from the Latin word which means below. Thus, infrared means below red, indicating its position in the electromagnetic spectrum. Red is the color of visible light; infrared is invisible to the human eye. Visible light has a range of wavelengths that are manifested in the seven colors of a rainbow, with red having the longest wavelength and violet, the shortest. Similarly, infrared is divided into three general sections based on wave length and density: short-wave, high-density radiation of 1.2 to 1.3 microns; medium-wave, medium-density radiation of 2.5 to 3.8 microns; and long-wave, low density radiation that measures 3.8 to 6.0 microns. Alternative terms are near, medium and far infrared, with near infrared being nearer to the visible light side of the spectrum and far, or long-wave, infrared being close to the microwave zone.

The majority of remote control devices in homes today use infrared. Basically, an infrared remote control uses infrared light to carry signals between a remote control transmitter and the apparatus it’s commanding. The transmitter sends out light in pulses. These are translated into binary codes that have corresponding commands. The infrared receiver is positioned in front of the apparatus, where it receives these pulses of light and then decodes them into binary data understood by the microprocessor inside the apparatus. The microprocessor then translates the data into specific commands which it goes on to implement.

Objects emit heat or energy, one of the most easily discernible forms of energy is infrared. When an object is not hot enough to give off visible light, it emits most of its energy in the infrared spectrum. It is this heat that affords infrared numerous applications in almost every sector of life.

Converting infrared energy (also known as radiant heat) into an image that the human eye can see and understand is the process called thermal imaging. This is achieved with the use of an infrared camera that accurately measures temperature and translates it into color. Infrared imaging will show the warmest areas in a human body as red, followed by yellow, green, blue, and violet — violet being the least warm part. By studying how body heat is distributed, thermal imaging allows health practitioners to analyze body tissue and fluid to detect injury or disease.

Infrared light is also used in night vision equipment to add to ambient light sources, thus allowing visibility even in the dark. The military uses infrared sensors to locate and track targets or to detect hidden land mines or arms caches. Infrared sensors on satellites are used for environmental monitoring, pinpointing areas of pollution or fire or deforestation. Search and rescue operations use infrared sensors extensively to locate missing persons lost in the forest or jungle. People trapped in collapsed buildings or survivors of disasters are more easily located with the use of infrared as well.

To the delight of astronomers, galaxies light years away are now made visible through infrared. Archaeologists also use infrared to discover ancient settlements. Infrared is being used to preserve, restore, and conserve valuable historical and artistic works as well. Invisible details of ancient fragments and images painted under paintings are being brought to light through the use of infrared. In industry, thermal imaging is invaluable in testing and monitoring mechanical systems.