Visible light waves are the only electromagnetic waves we can see. We see these waves as the colours of the rainbow. Each colour has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. Modern science has incorporated the visible light spectrum into many electronic devices in use today. Every device that has a viewable screen creates and emits visible light, which your eye perceives as a picture. Such technologies include LCD computer monitors, cell phone screens and TV screens.

The human eye can only see a small range of light wavelengths called the spectrum. We cannot see infrared light. It lies beyond the visible light spectrum. But you can take photographs with an infrared filter or infrared film, which produces intriguing effects, to peer into this world. Colours and textures take on unique properties when reflected with infrared light, also known as IR light.

Robert Wood published the first infrared images in 1910. His photos were shot on experimental film that required very long exposures. For that reason, most of his subjects were landscapes. In World War I, infrared photos proved invaluable. The images could pierce the toxic gas that polluted the air. Troops were better able to determine differences between buildings, vegetation, and water to gather crucial intel. In the thirties, Kodak and other camera manufacturers commercially released infrared film to the general public.

In the Second World War infrared could distinguish between camouflage and real trees and undergrowth. The military continued its research into IR photography. It became a vital tool for modern warfare.

Two decades later, recording artists like Jimi Hendrix and the Grateful Dead further popularised the technique. They released album covers with infrared images that were popular due to their multicoloured look. Now, the genre no longer requires special film to capture the images. Modern cameras and filters have made digital infrared photography more accessible than ever.

When light passes from one material to another material with a different density, is usually bends or changes course and this makes lens design extremely difficult as different colours of light bend by slightly different amounts but need to focus on the same point for the photograph. When blue light passes from air through a dense glass prism, for example, it bends slightly more than red light does. This is why a prism breaks white light up into a rainbow of different colours as each colour bends to a different angle. The air and even raindrops bend the wavelengths to different amounts, causing rainbows when sunlight passes through.

Human visible light waves have wavelengths between about 400 and 700 nanometers (4,000 to 7,000 angstroms) as noted before in my chart. Our eyes perceive these different wavelengths of light as the rainbow hues of colours. Human visible red light has relatively long waves, around 700 nm long. Blue and purple light have short waves, around 400 nm. Shorter waves vibrate at higher frequencies and have higher energies. Red light has a frequency around 430 terahertz, while blue's frequency is closer to 750 terahertz. Red photons of light carry about 1.8 electron volts (eV) of energy, while each blue photon transmits about 3.1 eV. I use the term human visible as animals often see other wavelengths.

Human visible light's neighbours on the EM spectrum are infrared radiation on the one side and ultraviolet radiation on the other and some animals and insects can see these wavelengths.

Infrared radiation has longer waves than red light, and thus oscillates at a lower frequency and carries less energy. Ultraviolet radiation has shorter waves than blue or violet light, and thus oscillates more rapidly and carries more energy per photon than visible light does.