The Electromagnetic Spectrum

The electromagnetic spectrum shows the relationship of varying forms of energy including the visible light that we see with our eyes. All energy in the spectrum moves at the speed of light. As you go to the right on the chart below the wavelength increases. If you draw a wave the distance between the peaks of each wave is known as it's wavelength.

electromagnetic spectrum


Gamma Rays and X-Rays

These rays have the shortest wavelength and produce a tremendous amount of energy. Gamma ray and X-ray waves can penetrate most objects.

Ultraviolet, Visible and Infrared Energy

Visible light is a very narrow portion of the entire spectrum. Infrared energy is very similar to visible light but is usually associated with heat. All objects radiate infrared energy.

Microwaves and Radio Waves

These are the longest of waves. Radio waves can reach wavelengths of 1 kilometer or more. Radio waves can be used to image distant objects.


The History of Electromagnetism

Electric charges as well as current and magnetism exert influence across space. In 1873 James Clerk Maxwell published his theory that electromagnetism moves across space at the speed of light in waves identical to those of light except for their wave lengths. In 1888 Heinrich Hertz detected such waves. Guglielmo Marconi used these discoveries in developing the radio.


Radiant heat and other radiations were found to conform to Maxwell's theory. Together they make up the electromagnetic spectrum. This seemed to prove that all radiant energy moves in waves. However, another phase of Hertz's work (and work done by others) revived the particle theory.

During his experiments, Hertz had found that light falling upon metal would drive out a negative charge. (This phenomenon is called the photoelectric effect.) Further experiments suggested that the charge might consist of particles. Evidence of particles was also being found in electric discharges through a vacuum; and in 1896 Antoine Henry Becquerel discovered the natural radioactivity of uranium. Shortly after, Marie and Pierre Curie discovered radioactive polonium and radium. Studies revealed that there were three kinds of radioactive rays, called alpha, beta, and gamma. Alpha rays were found to be positively charged particles; beta rays were negative particles; and gamma rays were electromagnetic pulses that carried more energy than the X rays discovered by Wilhelm Roentgen in 1895.


Other experimenters proved that electrons exist and that they are one of the building blocks with which atoms are constructed. Beta rays were proved to be electrons. By 1900 it was clear that atoms are made of smaller electrified particles. It also became clear that free electrons exert a negative charge; and electric current consists of electrons moving through a conductor. Thus electricity and atoms are intimately connected, and both are particles in nature.


What part of the electromagnetic spectrum is ideal for an IR camera?

As Temperatures rise the wavelength in the infrared spectrum being emitted decreases until it eventually becomes visible to the naked eye like a hot stove or a light bulb filament. Going by this theory alone a short wave IR camera will perform better for higher temperature analysis.

Today's Technology

Thermal cameras have come a long way from old bulky units that required liquid nitrogen to operate and produced fuzzy images. The latest generation of thermal imagers are extremely reliable high resolution hand held devices. These cameras can be calibrated to service a wide array of applications or they can be custom designed to fit your unique situation. There are instances when certain wavelength camera will be the most appropriate for your needs. Most of the time that will not be the primary concern and other factors such as feature set, image quality and budget will take precedence. Many cameras can perform a multitude of tasks and may be more appropriate for your budget and overall objectives.