acronym A word made by combining some of the starting letter or groups of letters from a number of words. For instance, STEM is an acronym for Science, Technology, Engineering and Math. Radar is an acronym for RAdio Detection And Ranging. Even laser is an acronym for Light Amplification by Stimulated Emission of Radiation.
atom The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
crystal (adj. crystalline) A solid consisting of a symmetrical, ordered, three-dimensional arrangement of atoms or molecules. It’s the organized structure taken by most minerals. Apatite, for example, forms six-sided crystals. The mineral crystals that make up rock are usually too small to be seen with the unaided eye.
current A fluid — such as of water or air — that moves in a recognizable direction. (in electricity) The flow of electricity or the amount of electricity moving through some point over a particular period of time.
electron A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.
excite (in chemistry and physics) To transfer energy to one or more outer electrons in an atom. They remain in this higher energy state until they shed the extra energy through the emission of some type of radiation, such as light.
laser A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.
liquid A material that flows freely but keeps a constant volume, like water or oil.
particle A minute amount of something.
photon A particle representing the smallest possible amount of light or other type of electromagnetic radiation.
physics The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in such areas is known as a physicist.
radiation (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
wavelength The distance between one peak and the next in a series of waves, or the distance between one trough and the next. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves.