photons
121Photoelectric effect — The photoelectric effect is a quantum electronic phenomenon in which electrons are emitted from matter after the absorption of energy from electromagnetic radiation such as x rays or visible light.cite book | title = Physics for Scientists… …
122Population inversion — In physics, specifically statistical mechanics, a population inversion occurs when a system (such as a group of atoms or molecules) exists in state with more members in an excited state than in lower energy states. The concept is of fundamental… …
123Time travel — This article details time travel itself. For other uses, see Time Traveler. Time travel is the concept of moving between different moments in time in a manner analogous to moving between different points in space, either sending objects (or in… …
124Lambert's cosine law — See also: Lambertian reflectance In optics, Lambert s cosine law says that the radiant intensity observed from a Lambertian surface or a Lambertian radiator is directly proportional to the cosine of the angle θ between the observer s line of… …
125Quantum cryptography — Quantum cryptography, or quantum key distribution (QKD), uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random bit string known only to them, which can be used as a key to encrypt and decrypt… …
126Raman scattering — or the Raman effect (pronounced: IPA| [rə.mən] ) is the inelastic scattering of a photon. Discovered By Dr. C.V. Raman in liquids and by Grigory Landsberg and Leonid Mandelstam in crystals.When light is scattered from an atom or molecule, most… …
127Apache Point Observatory Lunar Laser-ranging Operation — APOLLO shooting a laser at the Moon. The laser pulse is reflected from the retroreflectors on the Moon (see below) and returned to the telescope. The round trip time tells the distance to the Moon to great accuracy. In this picture the Moon is… …
128Quantum eraser experiment — In physics, the quantum eraser experiment is a double slit experiment that demonstrates several laws of quantum mechanics, including wave particle duality, which seeks to explain certain wave and particle properties of matter, complementarity,… …
