18WuD2x

electronic watch • electron stream 249
motor driven by a stable oscillator. 2. Any miniature
timepiece incorporating solid-state circuitry,
but especially one using a digital readout.
electronic wattmeter A wattmeter in which an
amplifier is used for increased sensitivity.
electronic waveform synthesizer A signal generator
that delivers an alternating or pulsating signal
whose waveform can be tailored by means of
adjustable circuit components.
electron lens A device that focuses an electron
beam in a manner similar to the focusing of light
rays by a glass lens. Also see ELECTROSTATIC
LENS, ELECTROMAGNETIC LENS, and WAVE-
GUIDE LENS.
electron magnetic moment The energy per unit
flux density available in an electron. Approximately
equal to 9.2848 × 10 –24 joule per tesla.
electron mass See MASS OF ELECTRON AT REST.
electron microscope A microscope in which the
source of illumination is an electron beam focused
by electromagnetic lenses. It allows much
greater magnification than is possible with optical
microscopes.
Image
Electron gun
Object
+dc
Magnetic lens
Magnetic lens
Image
Magnetic lens
Fluorescent
screen
electron microscope
electron mirror A reflector of electrons—especially
a dynode element in a photomultiplier tube or
electron-multiplier tube.
electron motion 1. The movement of electrons in
a conductor, semiconductor, or space, as the
result of electric or magnetic attraction or
repulsion. 2. The movement of an electron as a
charged mass. In an electric field, this movement
simulates that of a free-falling body in a gravitational
field.
electron multiplication 1. In a gas discharge, the
production of additional electrons as a result
of collisions between electrons, atoms, and
molecules. 2. The increased production of electrons
in a semiconductor when avalanche occurs.
electron-multiplier tube 1. A vacuum tube utilizing
a sequence of secondary emissions for increased
current amplification. Electrons from the
cathode strike a positively biased dynode with a
force that dislodges secondary electrons, which,
upon joining those first emitted, are reflected to a
second positive dynode that contributes more
secondary electrons, reflecting the total to a third
positive dynode, etc. The last dynode in the chain
reflects the enhanced beam to an anode collector
that passes the high current to an external circuit.
2. See PHOTOMULTIPLIER TUBE.
electronography Printing by means of the electrostatic
transfer of ink from a printing plate across
a gap to an impression cylinder.
electron optics See ELECTRO-OPTICS.
electron orbits See ELECTRON SHELLS.
electron oscillator A device in which oscillation is
obtained by causing electrons to move in an oscillatory
path, to travel in bunches, etc. Examples:
klystron, magnetron, and traveling-wave
tube.
electron pair Two electrons from adjacent atoms,
which sometimes share the same orbits, but always
produce a bond between two adjacent
atoms.
electron-pair bond The bond between an electron
pair.
electron physics The physics of electronics, usually
from a highly theoretical viewpoint.
electron-proton magnetic moment ratio A physical
constant whose value is approximately equal
to 658.211, derived from the division of the magnetic
moment of the electron by that of the proton.
electron recoil The recoil of an electron from a
photon it has collided with.
electron rest mass See MASS OF ELECTRON AT
REST.
electron scanning Deflection of an electron beam.
See, for example, ELECTROSTATIC DEFLEC-
TION and ELECTROMAGNETIC DEFLECTION.
electron shells The spheres, concentric with the
nucleus of an atom, that represent the median
distances from the nucleus around which electrons
migrate.
electron spin The rotation of an electron (i.e.,
around its axis). This motion is independent of
the electron’s movement around the nucleus of
an atom.
electron stream 1. The beam of electrons generated
by the electron gun in a cathode-ray tube.