| Glossary | ||||||||||||||
absolute zero — lowest possible temperature matter can have, corresponding to the minimum energy that its atoms or molecules can have; the zero point of the Kelvin temperature scale. absorption — (1) process by which a wave loses energy to a material as it passes through it; (2) process by which the electron of an atom takes in the energy of a photon of light, thereby increasing the electron’s energy and moving it to a higher energy level. acceleration — rate of change in velocity or the change in velocity divided by the change in time. Units of acceleration are units of speed divided by units of time, or m/s2 (sometimes written as m/s/s). accuracy — how well a measurement’s value agrees with a commonly accepted value. additive primary colors (RGB) — three colors (red, green, and blue) that, when added together in various combinations, can create any other color. Also called the additive color process. adiabatic process — thermodynamic process in which no heat is added or removed from a system. Because no heat is exchanged, an adiabatic process is reversible. alpha decay — radioactive decay in which a nucleus emits an alpha particle (consisting of two protons and two neutrons), thereby reducing the original atom’s atomic number by two. ampere (A) — unit of electric current, equivalent to one coulomb of charge per second. amplitude — maximum displacement of an oscillation from its equilibrium, or average, value. angle of incidence — angle between a light ray that strikes a surface and the normal to the surface at the point of contact. angle of reflection — angle between a light ray that reflects off a surface and the normal to the surface at the point of reflection. angular momentum — momentum of an object due to its rotation or spin. Angular momentum is the product of the radius of rotation and the momentum, or L = r × mv. Angular momentum has units of kg m2/s. | angular velocity
— rate at which a body rotates about an axis or center. Units are radians per second (rad/s). antinode — point of maximum amplitude on a standing wave. armature — rotating part of an electric motor containing electromagnets. atom — smallest particle of an element that can exist in isolation or in a combination with other atoms. Consists of a heavy nucleus surrounded by one or more electrons. atomic mass unit (amu) — standard unit of measure for expressing the mass of an atom. One amu is defined as one-twelth of the mass of a carbon-12 atom or 1.661×10−27 kg. atomic number — number associated with an atom that is equal to the number of protons in its nucleus. average velocity — distance or displacement an object travels divided by the time taken, regardless of any variations in velocity during the time interval. Avogadro’s number — 6.022×1023 particles, the number of particles in one mole. axis — (1) imaginary straight line about which an object rotates; (2) one of the reference lines used to depict a coordinate system. battery — device that transforms or converts chemical energy into electrical energy or electric current. A battery’s voltage, or potential difference, is measured in volts (V). beats — pulsations of sound resulting from the superposition of two waves of different frequencies. The beat frequency is the difference in frequency between the two waves. Bernoulli’s equation — expression of energy conservation along a streamline for a frictionless fluid. Often expressed as ρgh + ½mv2 + P = constant. beta decay — radioactive decay in which a neutron in the nucleus of an atom spontaneously converts into a proton and an electron. The proton remains in the nucleus, increasing the atom’s atomic number by one, while the energetic electron is emitted as a beta particle. | |||||||||||||
| ||||||||||||||
