Light energy is a form of energy and is expressed in joules. Light, in physics, is the electromagnetic radiation of any wavelength; nevertheless, the definition of light is sometimes restricted to a specific range of wavelength (about 400-700 nm) that is visible to an unaided human eye. The latter is particularly referred to as visible light of the electromagnetic spectrum. The visible light is that part of the electromagnetic spectrum that is associated with the sense of sight in animals as well as photosynthesis in plants and other photosynthetic organisms. As for the sense of sight, sunlight, for instance, is screened out by the atmosphere of the earth while allowing the visible light to pass through. It is the visible light that is detected by the human eye. It is also the visible light that drives photosynthesis. Blue and red wavelengths are the chlorophylls' two most effectively absorbed wavelengths of the visible light.
Some organisms are capable of emitting light. This ability is called bioluminescence.
Word origin: Old English lēoht, cognate with Dutch licht, German Licht
- electromagnetic energy
- radiant energy
- luminous energy