In physics, light refers to electromagnetic radiation. The light we normally talk about in everyday life refers to the visible spectrum (the part of the electromagnetic spectrum that the human eye can see).
Other animals can see parts of the spectrum that humans can’t. For example, a large number of insects can see ultraviolet (UV) light.
UV light can be used to show things the human eye can’t see, coming in handy for forensic scientists.
The wavelength of infrared light is too long to be visible to the human eye.
Scientists study the properties and behaviors of light in a branch of physics known as optics.
Isaac Newton observed that a thin beam of sunlight hitting a glass prism on an angle creates a band of visible colors that includes red, orange, yellow, green, blue, indigo and violet (ROYGBIV). This occurred because different colors travel through glass (and other mediums) at different speeds, causing them to refract at different angles and separate from each other
Light travels very, very fast. The speed of light in a vacuum (an area empty of matter) is around 186,000 miles per second (300,000 kilometres per second).
Light travels slower through different mediums such as glass, water and air. These mediums are given a refractive index to describe by how much they slow the movement of light. Glass has a refractive index of 1.5, meaning that lights travels through it at around 124,000 miles per second (200,000 kilometres per second). The refractive index of water is 1.3 while the refractive index of air is 1.0003, meaning that air only slightly slows down light.
One of the many things Italian scientist Galileo Galilei worked on was telescopes, producing telescopes with around 30x magnification in some of his later work. These telescopes helped him discover the four largest moons orbiting Jupiter (later named the Galilean satellites).
Photosynthesis is a process that involves plants using energy from sunlight to convert carbon dioxide into food.