Laser

A laser is a device that emits light through a specific mechanism for which the expression laser is an acronym: Light Amplification by Stimulated release of Radiation. This is a combined quantum-mechanical and thermodynamical procedure discussed in more detail below. As a light source, a laser can have various properties, depending on the reason for which it is designed and calibrated. A typical laser emits light in a contracted, low-divergence beam and with a well-defined wavelength. This is in contrast to a light source such as the incandescent light bulb, which emits into a large solid angle and over a wide spectrum of wavelength. These properties can be summarized in the term coherence.

Light of a specific wavelength that passes through the increase medium is amplified; the neighboring mirrors ensure that the majority of the light makes many passes through the gain medium. Part of the light that is between the mirrors passes through the partially apparent mirror and appears as a beam of light. The process of supplying the power required for the amplification is called pumping and the energy is typically supplied as an electrical current or as light at a diverse wavelength. Most practical lasers contain additional elements that affect properties such as the wavelength of the emitted light and the form of the beam.

Science

Science refers to any systematic knowledge or practice. In a more restricted sense, science refers to a system of acquiring knowledge based on the scientific method, as well as to the organized body of knowledge gained through such research. This article focuses on the more restricted use of the word.

Fields of science are commonly classified along two major lines:

• Natural sciences, which study natural phenomena (including biological life), and
• Social sciences, which study human behavior and societies.


These groupings are empirical sciences, which mean the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.