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.
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.

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