Light Energy: What It Is and How It Works

light-energy Credit: Martin Fisch/CC-BY-SA 2.0

Light energy is a type of kinetic energy that consists of waves. It results from electromagnetic radiation and is the only form of energy visible to the human eye.

The Basics of Light Energy

All matter consists of some kind of energy. At its most basic, light is a form of energy transfer due to electromagnetic radiation. Light energy consists of photons, which are essentially tiny packets of energy. When an object's atoms heat up, it results in the production of photons, which is how photon production occurs in most cases. Usually, electrons absorb and destroy photons. However, if heat causes the electrons in atoms to become "excited" due to electromagnetic energy, then those electrons will emit photons on their own. An object emits more photons as it gets hotter. Light energy sources include the sun, stars, fire and light bulbs.

How Light Becomes Visible

When light travels, it is in the form of a wave. However, no material or matter is necessary to carry the energy along for the ride. Because of this, light can travel through a space that has no air. This differs from sound waves because they have to pass through a liquid, a solid or a gas. Light energy is the fastest known form of energy. When traveling through a vacuum, the speed of light is equal to 186,282 miles, or almost 300,000 kilometers, per second. Human eyes contain cells that can pick up different wavelengths. Light waves include many different wavelengths. Red has a wavelength of 700 nanometers, whereas violet is much shorter at 380 nanometers. These are perceived as different colors by the human eye. Hotter objects produce shorter wavelengths, which is why hotter objects appear blue. Some forms of light are invisible to the eye as their wavelengths are too long or too short to be perceivable.

Uses for Light Energy

Natural light on its own is useful. The human eye uses light waves to see. When light enters the cornea, it bends the light waves through the pupil. The iris opens and lets the light in through the retina and optic nerve. Devices such as cameras synthesize the processes that the eye uses to capture light and transform it into images.

However, light energy can be harvested for many other purposes. It can be reflected, refracted or harvested to view objects. Mirrors and glasses are basic forms of this technology, but the same principle can also help engineers build devices such as telescopes, which can view objects that are very far away. Lasers, which contain very bright lights, have a wide variety of purposes, including medicine, industrial production and computer technology.

Light energy from the sun can also create electricity. Solar panels contain smaller cells, which in turn contain minerals that absorb light energy from the sun. As solar panels absorb the energy, electrons in the molecules start to become loose due to their interactions with the photons from the sun's rays, which creates an electric charge. Wiring in panels picks up the electric charge and lets it flow through an electrical system or into a grid.