Infrared light is part of the electromagnetic spectrum that includes visible light and behaves similarly to visible light.  It can travel through space; it can be reflected, emitted and absorbed.  Infrared is next to visible light on the electromagnetic spectrum, between .7 µm (millionths of a meter) and 1000µm (or 1mm)  while visible light is only from  .4 µm to about .75 µm.  The measurements refer to the wavelength or frequency of the electromagnetic wave.        


This picture shows the electromagnetic spectrum and the size of the electromagnetic wavelength size compared to different objects.

Other types of electromagnetic radiation are Gamma rays, X-rays, Ultraviolet, microwaves, and radio waves.  Radio waves have the longest wavelengths that can be longer than a football field while Gamma waves have the shortest that are as small as the nucleus of an atom. 

We see in the visible light spectrum.  Our eyes can distinguish the different wavelengths of visible light that we recognize as different colors.  When light strikes an object that portion that is not absorbed by it is reflected.  That is what we see and perceive as the color of that object. 

In 1800 sir William Herschel, an astronomer wanted to find out which color(s) of light were responsible for heating objects.  In an experiment which consisted of using a prism to break the light into its different wavelengths, he moved thermometers with blackened bulbs through the different colors.  He noted an increase in temperature as he moved from violet to red.  Then he found that the highest temperature was actually just beyond the red light.  He called this invisible radiation “Calorific rays”.  Today we know them as infrared, which means below red.

Unlike visible light, Infrared radiation is emitted by every object that has any atomic motion, or in other words any object that is above absolute zero(-459.67°F or -273.16°C) which is the temperature at which atoms stop moving.  The higher the temperature of an object the more energy the atoms have and hence the more thermal energy that objects emits.  This thermal energy is what an infrared camera detects.  Since Thermal energy moves from warmer objects to colder objects we are able to see in the infrared spectrum the different heat levels of objects. 

Just like visible light has a range of wavelengths that run from violet to red, infrared has a range of wavelengths. “Near Infrared” is closest to visible light and “Far infrared” is closer to the microwave region of the electromagnetic spectrum.

Far infrared waves are thermal; we can feel them when we stand in the sunlight or in front of a hot radiator.    Near infrared are not hot at all.  These shorter wavelengths are the ones used by your TV remote control. 

Different wavelengths of infrared radiation are more useful than others.  The atmosphere absorbs infrared light at different amounts across the infrared spectrum
 


Commercial infrared cameras use one of 2 sections of the infrared spectrum the 3-5 micrometer band and the 8-12 micrometer band, because these 2 bands have the greatest atmospheric transmittance.  There are other cameras used by scientists to peer into outer space but they are of limited use inside the atmosphere of the earth. 

Because everything emits infrared energy, being able to see it is very important as it tells us information about things that we can not see with our eyes.    Astronomers use infrared telescopes to see into the far reaches of outer space.  Being able to see the universe in infrared has lead to many new discoveries about it.

 
Eagle Nebula taken by Spitzer space telescope

Infrared has many uses in the building and maintenance fields.  Because electrical and mechanical equipment often overheat before failing, being able to record and analyze infrared data can detect failing equipment before it fails, saving many times the cost of an infrared survey.


Motor in front is normal temperature. Motor in rear has defective windings causing it to run hot and use more energy!



On a clear night a flat roof will cool off quickly where it is dry but where there is wet insulation under roof membrane it takes longer to cool creating a dramatic difference in temperature.

Mariners can use it to see their way in complete darkness.  Rescues at sea at night become much easier when you can see the heat of the person in the water.  Some cars now come equipped with forward looking infrared cameras, extending the range of vision far beyond the headlights.  Veterinarian's use infrared imaging to diagnoses some animals.  Medical doctors are beginning to use infrared to diagnose a variety of ailments.  Firefighters use it to see through the thick smoke of a fire.  The weather service has long used infrared to help forecast the weather.

Contact us today to find out how infrared can help you!