Plants generally grow best under sunlight. This is because the sun's light contains more energy and is more evenly distributed than artificial light. In particular, the sun emits a broader spectrum of light that contains more coverage in the red and blue regions, whereas artificial light typically lacks these.
Visible light is a type of electromagnetic radiation that is between 400 and 700 nanometers in wavelength. Other types of light, such as infrared and ultraviolet, have different wavelengths. Infrared light has longer wavelengths than visible light, while ultraviolet light has shorter wavelengths.
The speed of light in a vacuum is considered a constant of the universe at approximately 186,000 miles per second. This speed is great enough to circle the Earth in less than eight seconds. Physicists often refer to other kinds of electromagnetic radiation as light, even if it is not visible, infrared or ultraviolet. Thus, gamma rays, x-rays, microwaves and radio waves are all types of light and travel at the same speed.
Light is composed of photons, or massless individual units that demonstrate behavior similar to both particles and waves. Despite a lack of mass, photons are able to exert pressure through a transfer of momentum. This holds great potential for future technology in switches, windmills, asteroid defense and space travel.