Light is a form of electromagnetic radiation. It is the natural agent that stimulates sight and makes things easy to see.
It has a wavelength which can be seen by the human eye. Animals can also see light. Light makes up a small part of both the electromagnetic spectrum and radiation given off by stars like the sun. The study of light is known as optics. When light hits an opaque object, it makes a shadow. When light hits a transparent object, it passes through it almost completely without making a shadow.
Light is a form of electromagnetic radiation that shows properties of both waves and particles. It is a form of energy. Light also keeps the Earth warm. Light exists in tiny energy packets called photons. Each wave has a wavelength or frequency. The human eye sees each wavelength as a different color. Rainbows show the entire spectrum of visible light. The separate colors, moving in from the outer edges, are red, orange, yellow, green, blue, indigo and violet. Other colors can be seen only with special cameras or instruments: Wavelengths below the frequency of red are called infrared, and higher than of violet are called ultraviolet.
In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. This article is about visible light. Read the electromagnetic radiation article for the general concept.
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