Light of my Life is not the light of your life
It was Isaac Newton who from series of experiments postuated that light is a spectrum of 7 colors. We also believe from the colors we see in a rainbow. The red light along one edge of the rainbow is electromagnetic radiation with a wavelength of about 620 to 750 nanometres; the violet light along the opposite edge is radiation with a wavelength of 380 to 450nm.
But there is far more to electromagnetic radiation than these visible colours. Light with wavelengths slightly longer than the red light we see is called infrared. Light with wavelengths slightly shorter than violet is called ultraviolet.
Many animals can actually see ultraviolet, and so can some people, says Eleftherios Goulielmakis of the Max Planck Institute of Quantum Optics in Garching, Germany. In some circumstances even infrared is visible to humans.
Beyond ultraviolet, electromagnetic wavelengths can go shorter than 100nm. This is the realm of X-rays and gamma rays. You won’t often hear X-rays described as a form of light.
“A scientist wouldn’t say ‘I’m shining X-ray light on the target’. They would say ‘I’m using X-rays’,” says Goulielmakis.
Meanwhile, go beyond infrared and electromagnetic wavelength stretches to 1cm and even up to thousands of kilometres. These electromagnetic waves are given familiar names like microwaves and radio waves. It may seem strange to think of the radio waves used in broadcasting as light.
“There is no real physical difference between radio waves and visible light from the point of view of physics,” says Goulielmakis. “You would describe them with exactly the same sort of equations and mathematics.” It’s only our everyday language that treats them as different.
So we have another definition of light. It is the very narrow range of electromagnetic radiation that our eyes can actually see. In other words, light is a subjective label that we only use because our senses are limited.