Light is made up of electromagnetic particles that travel in waves. These waves emit energy, and range in length and strength. The shorter the wavelength; the higher the energy. The length of the waves is measured in nanometers (nm), with 1 nanometer equaling 1 billionth of a meter. Every wavelength is represented by a different colour, and is grouped into the following categories: gamma rays, x-rays, ultraviolet (UV) rays, visible light, infrared light, and radio waves. Together these wavelengths make up the electromagnetic spectrum.
However the human eye is sensitive to only one part of this spectrum: visible light. Visible light is that part of the electromagnetic spectrum that is seen as colours: violet, indigo, blue, green, yellow, orange and red. Blue light has a very short wavelength, and so produces a higher amount of energy. Studies suggest that, over time, exposure to the blue end of the light spectrum could cause serious long-term damage to your eyes.