Elodea is called ditch moss or waterweed. Elodea is commonly used in aquariums to keep the oxygen balanced because when exposed to light oxygen is produced. The energy of light is called radiant energy. Light contains colors with different wavelengths. Light is measurable with nanoseconds or billions of seconds.
Light is a type of electromagnetic wave that causes a visual sensation when it strikes the retina.
Light then is also some thing humans need to survive. 1995 volume P, pp.