Light is made up of electromagnetic particles that travel in waves. These light waves emit energy and vary in length and strength. The shorter the wavelength; the higher the amount of energy. 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.
Blue light is emitted by the sun, digital screens (TVs, computers, laptops, smart phones and tablets), electronic devices, and fluorescent and LED lighting!