Light

Visible light is everything you see, and comes in the form of waves. Your eyes are attuned to a range of wavelengths from the electromagnetic spectrum, and the electromagnetic waves which have wavelengths within that range are perceptible by your eyes and interpreted by our brains as visible light. The specific range of wavelengths which is generally considered perceptible by homosapiens (a.k.a. humans) is 380 to 750 nanometers. Light waves of smaller wavelength (e.g. less than 380 nanometers in wavelength) are also known as ultraviolet light, and light of larger wavelength is also known as infrared light. When light waves with wavelengths within this range interact with the light cones in human eyes, the human brain sends electrical signals to the brain, the latter of which then interprets these electrical signals as what is generally referred to as the light which we perceive with our eyes.

More specifically, visible light is composed of only a small range of a much larger spectrum, that of electromagnetic radiation. Radiation is another important concept to have an understanding of in the sciences, particularly when it comes to nuclear physics, but will not be elaborated on here aside from recognition of the notion that light waves can be seen (from a certain perspective) as being quantized packets/particles called photons, and all electromagnetic radiation can be said to be composed of these photons. All "particles" can also be considered to be "waves", hence photons are also light waves; the concept of wave-particle duality will not be elaborated on here, but is an important concept to be aware of when working with knowledge pertaining to our current (i.e. 2025 A.D.) understanding of the physical sciences.