Absolute Zero - The lowest possible temperature
in the universe, at which all atomic activity ceases. Equal to
-273 degrees Celsius (- 459 degrees Fahrenheit). Used as a
benchmark for measuring temperature.
Accelerator - A machine that serves as a source
for a well-defined beam of high speed particles for studies in
nuclear science and high energy (or particle) physics.
Angstrom - Abbreviated Å. A unit of length
equal to 10-8 cm (one-hundredth of a millionth of a centimeter).
An Angstrom is on the order of the size of an atom.
Antiparticle - A metal that when cooled below a
critical temperature has a total disappearance of electrical
resistance. Twenty-five elements and many alloys and compounds
have been found to be superconducting. The critical temperatures
range from .002 k to 18K Arc Degree - A unit of angular measure in
which there are 360 arc degrees in a full circle.
Arc Second - Abbreviated arcsec. A unit of
angular measure in which there are 60 arc seconds in 1 arc
minute and therefore 3600 arc seconds in 1 arc degree. One arc
second is equal to about 725 km on the Sun.
Atom - A point-like particle with a
negative charge; member of the lepton group and thus not
divisible into more fundamental particles.
Accuracy - Closeness of a measurement to the
standard value of that quantity.
Achromatic Lens - Lens for which all light colors
have the same focal length.
Action-Reaction Forces - Pair of forces involved in an
interaction that are equal in magnitude and opposition in
direction. Activity - Number of decays per second of a
radioactive substance. Adhesion - Force of attraction between two
unlike materials. Air
Resistance - Force of air on objects moving
through it. Alpha Decay - Process in which a nucleus emits
an alpha particle. Alpha
Particle - Positively- charged particles
consisting of two protons and two neutrons emitted by
radioactive materials. Ammeter - Device to measure electrical
current. Amorphous solid - Solids that have no long range
order; no crystal structure.
Ampere - Unit of electric current; one
ampere is the flow of one coulomb of charge per second.
Amplitude - In any periodic motion, the
maximum displacement from equilibrium.
Angle of Incidence - Angle between direction of motion
of waves and a line perpendicular to surface the waves are
striking. Angle of
Reflection - Angle between direction of motion
of waves and a line perpendicular to surface the waves are
reflected from. Angle of
Refraction - Angle between direction of motion
of waves and a line perpendicular to surface the waves have been
refracted from. Angular
Momentum - Quantity of rotational motion.
For a rotating object, product of moment of inertia and angular
velocity.
Annihilation - Process in which a particle and
its antiparticle are converted into energy.
Antenna - Device used to receive or
transmit electromagnetic waves.
Antineutrino - Subatomic particle with no charge
or mass emitted in beta decay.
Antinode - Point of maximum displacement of
two superimposed waves. Archimedes’ Principle - Object immersed in a fluid has an
upward force equal to the weight of the fluid displaced by the
object. Artificial
Radioactivity - Radioactive isotope not found in
nature. Atomic mass unit - Unit of mass equal to 1/12 the
atomic mass of carbon- 12 nucleus.
Atomic number - Number of protons in the nucleus
of the atom. Average
Acceleration - Acceleration measured over a
finite time interval Average velocity - Velocity measured over a finite
time interval. |