Light: A Fundamental Force In Our World If asked what light is, one could say that it\'s one of the most basic elements of our world and our universe as we perceive it. It is through sight that we receive 90% of our information. It is through the use of telescopes aiding the naked eye that we are aware of the heavenly bodies around us. It is through light that the energy from the sun is transferred to us. The sun\'s energy supports the food chain; plants use it to turn water and CO2 into energy usable by other organisms. Solar energy was also used, indirectly, to produce all of the fossil fuels that we consume daily. Since light is such a basic part of our existence, we should have a basic understanding of what it is. What we call light, the intangible, powerful force that powers our world, is somewhat hard to define in real terms. It shares properties with both particles and waves. It follows the same rules as a wave does--it moves in a regular fashion, in a perfect sine wave at a certain frequency. It travels in a straight line, and is subject to refraction. All of these characteristics are found in waves of any type, from radio frequency waves, up to Gamma and X- rays. Light, however, also exhibits qualities characteristic of particles such as neutrons and protons. A photon, or quanta, is the "packet" of energy that is sent in a light wave. Like a particle, the photon is believed to have a finite mass, and has the ability to affect other matter. As light strikes a photovoltaic solar cell, it knocks electrons in the silicon atoms on the surface into a higher state of energy. When these return to their normal, or "ground" state, energy is produced in the form of electricity. Thus, light is termed a "wave- particle," and this property is called the "wave-particle duality of nature." Many questions concerning what makes up light still lie unanswered, but this much is thought to be true. Light can be produced in a variety of ways. Our sun, like other stars, uses nuclear fusion to produce energy in the form of light and radiation. We can produce light artificially using several methods. If one starts a fire, it produces light and heat. (Heat, which is infrared radiation, is another type of light energy.) The light and heat are a result of a chemical reaction, the combining of oxygen with the carbon in the wood. This reaction leaves behind products which have less potential energy than they started with. The energy, which left as light and heat, was produced when electrons dropped in energy levels during the reaction. The excess energy from one atom was given off as a photon, producing light. If one examines a fluorescent or incandescent light bulb, one can see that all it is doing is having electricity stimulate a metallic or gaseous substrate, causing it to give off photons. The principle is the same as it was with the fire, only it is more controlled. Still more controlled is the laser, which puts out its photons in a single frequency. This is achieved through a carefully designed apparatus which stimulates materials in a way that allows them to only put out light at a certain wavelength. Laser light is, therefore, of all one color. White light, or sunlight, is a broad mixture of wavelengths. All methods of producing light, natural and artificial, share one common feature: they rely on electrons changing energy levels to produce the photons. As there are a variety of methods of producing light, so are there a multitude of ways it can be applied. The most obvious use of light is in supporting our food chain. Without light energy, nothing could live on our planet. The plants, which are at the bottom of the food chain, supply energy to all other organisms. We as humans are adapted to having sunlight around us, and taking in information with our eyes. Aside from keeping us alive, light is also employed in highly specialized applications. Laser light is being used in surgery. The highly concentrated beam of light is far more precise than any surgeon\'s hand, and much finer than the