Flare (Solar) - Rapid release of energy from a
localized region on the Sun in the form of electromagnetic
radiation, energetic particles, and mass motions.
Flare Star - A member of a class of stars that
show occasional, sudden, unpredicted increases in light. The
total energy released in a flare on a flare star can be much
greater that the energy released in a solar flare.
Footpoint - The intersection of magnetic
loops with the photosphere.
Free Electron - An electron that has broken free
of it's atomic bond and is therefore not bound to an atom.
Frequency - The number of repetitions per
unit time of the oscillations of an electromagnetic wave (or
other wave). The higher the frequency, the greater the energy of
the radiation and the smaller the wavelength. Frequency is
measured in Hertz.
Factor-label method - Dimensional analysis.
Farad - Unit of capacitance. One coulomb
Materials - Materials in which large internal
magnetic fields are generated by cooperative action of
First Harmonic - In music, the fundamental
First law of
Thermodynamics - Change in internal or thermal
energy is equal to heat added and work done on system. Same as
law of conservation of energy.
Fluid - Material that flows, i.e.
liquids, gases, and plasmas.
Focal Length - Distance from the focal point to
the center of a lens or vertex of a mirror.
Focal Point - Location at which rays parallel
to the optical axis of an ideal mirror or lens converge to a
Forbidden Gap - Energy values that electrons in a
semiconductor or insulator may not have.
Force - Agent that results in
accelerating or deforming an object.
Frame of Reference - Coordinate system used to define
Fraunhofer Lines - Absorption lines in the sun’s
spectrum due to gases in the solar atmosphere.
Friction - Force opposing relative motion of
two objects are in contact.
Fundamental Particles - Those particles( i.e. quarks and
leptons) of which all materials are composed.
Fundamental Tone - Lowest frequency sound produced
by a musical instrument.
Fundamental Units - Set of units on which a
measurement system is based( i.e. meter, second, kilogram,
Fuse - Metal safety device in an
electric circuit that melts to stop current flow when current is
Fusion - Combination of two nuclei into
one with release of energy.