Symbols
-particles
6.4 Bohr’s Model of the Hydrogen Atom
A
aberration
2.2 Spherical Mirrors
absorber
6.1 Blackbody Radiation
absorption spectrum
6.4 Bohr’s Model of the Hydrogen Atom
acceptor impurity
9.6 Semiconductors and Doping
accommodation
2.5 The Eye
activity
10.3 Radioactive Decay
Albert Einstein
Introduction
ALICE detector
11.4 Particle Accelerators and Detectors
alpha (
) rays
10.4 Nuclear Reactions
alpha decay
10.4 Nuclear Reactions
amorphous solids
9.3 Bonding in Crystalline Solids
amplifier
9.7 Semiconductor Devices
angular magnification
2.7 The Simple Magnifier
angular momentum orbital quantum number
8.1 The Hydrogen Atom
angular momentum projection quantum number
8.1 The Hydrogen Atom
anti-symmetric function
7.1 Wave Functions
antielectrons
10.4 Nuclear Reactions
antineutrino
10.4 Nuclear Reactions
antiparticle
11.1 Introduction to Particle Physics
apparent depth
2.3 Images Formed by Refraction
atomic bomb
10.5 Fission
atomic mass
10.1 Properties of Nuclei
atomic mass unit
10.1 Properties of Nuclei
atomic nucleus
10.1 Properties of Nuclei
atomic number
10.1 Properties of Nuclei
atomic orbital
8.1 The Hydrogen Atom
B
Balmer formula
6.4 Bohr’s Model of the Hydrogen Atom
Balmer series
6.4 Bohr’s Model of the Hydrogen Atom
Bardeen
9.8 Superconductivity
baryon number
11.2 Particle Conservation Laws
base current
9.7 Semiconductor Devices
BCS theory
9.8 Superconductivity
Becquerel
10.3 Radioactive Decay
becquerels
10.3 Radioactive Decay
beta (
) rays
10.4 Nuclear Reactions
beta decay
10.4 Nuclear Reactions
Betelgeuse
6.1 Blackbody Radiation
Bethe
10.6 Nuclear Fusion
Big Bang
11.6 The Big Bang
binding energy (BE)
10.2 Nuclear Binding Energy
binding energy per nucleon (BEN)
10.2 Nuclear Binding Energy
birefringent
1.7 Polarization
blackbody
6.1 Blackbody Radiation
blackbody radiation
6.1 Blackbody Radiation
Blu-Ray player
8.6 Lasers
body-centered cubic (BCC)
9.3 Bonding in Crystalline Solids
Bohr magneton
8.2 Orbital Magnetic Dipole Moment of the Electron
Bohr model
8.1 The Hydrogen Atom
Bohr radius of hydrogen
6.4 Bohr’s Model of the Hydrogen Atom
Bohr’s model of the hydrogen atom
6.4 Bohr’s Model of the Hydrogen Atom
bond length
9.1 Types of Molecular Bonds
Born interpretation
7.1 Wave Functions
Brackett series
6.4 Bohr’s Model of the Hydrogen Atom
Bragg planes
4.6 X-Ray Diffraction
braking radiation
8.5 Atomic Spectra and X-rays
breakdown voltage
9.7 Semiconductor Devices
breeder reactor
10.5 Fission
Brewster’s angle
1.7 Polarization
Brewster’s law
1.7 Polarization
C
Cameras
2.6 The Camera
carbon-14 dating
10.3 Radioactive Decay
Cassegrain design
2.8 Microscopes and Telescopes
chain reaction
10.5 Fission
charge-coupled device (CCD)
2.6 The Camera
chart of the nuclides
10.1 Properties of Nuclei
chemical group
8.4 The Exclusion Principle and the Periodic Table
chromatic aberrations
2.4 Thin Lenses
cladding
1.4 Total Internal Reflection
classical (Galilean) velocity addition
5.6 Relativistic Velocity Transformation
coherent waves
3.1 Young's Double-Slit Interference
collector current
9.7 Semiconductor Devices
color
11.3 Quarks
complex function
7.1 Wave Functions
compound microscope
2.8 Microscopes and Telescopes
Compton
6.3 The Compton Effect
Compton effect
6.3 The Compton Effect
Compton shift
6.3 The Compton Effect
Compton wavelength
6.3 The Compton Effect
concave
2.4 Thin Lenses
concave mirror
2.2 Spherical Mirrors
conduction band
9.5 Band Theory of Solids
constructive interference
3.1 Young's Double-Slit Interference
converging lens
2.4 Thin Lenses
convex
2.4 Thin Lenses
convex mirror
2.2 Spherical Mirrors
Cooper
9.8 Superconductivity
Cooper pair
9.8 Superconductivity
Copenhagen interpretation
7.1 Wave Functions
cornea
2.5 The Eye
Cornell Electron Storage Ring
11.4 Particle Accelerators and Detectors
corner reflector
1.2 The Law of Reflection
cosmic microwave background radiation
11.7 Evolution of the Early Universe
cosmological principle
11.6 The Big Bang
cosmology
11.6 The Big Bang
critical angle
1.4 Total Internal Reflection
critical magnetic field
9.8 Superconductivity
critical mass
10.5 Fission
critical temperature
9.8 Superconductivity
criticality
10.5 Fission
curie (Ci)
10.3 Radioactive Decay
curved mirror
2.2 Spherical Mirrors
cut-off frequency
6.2 Photoelectric Effect
cut-off wavelength
6.2 Photoelectric Effect
cyclotron
11.4 Particle Accelerators and Detectors
D
dark energy
11.7 Evolution of the Early Universe
dark matter
11.7 Evolution of the Early Universe
daughter nucleus
10.4 Nuclear Reactions
Davisson
6.5 De Broglie’s Matter Waves
Davisson–Germer experiment
6.5 De Broglie’s Matter Waves
de Broglie
6.5 De Broglie’s Matter Waves
de Broglie wave
6.5 De Broglie’s Matter Waves
de Broglie’s hypothesis of matter waves
6.5 De Broglie’s Matter Waves
decay
10.3 Radioactive Decay
decay constant
10.3 Radioactive Decay
decay series
10.4 Nuclear Reactions
density of states
9.4 Free Electron Model of Metals
depletion layer
9.7 Semiconductor Devices
destructive interference
3.1 Young's Double-Slit Interference
destructive interference for a single slit
4.1 Single-Slit Diffraction
deuterium
10.1 Properties of Nuclei
diamonds
1.4 Total Internal Reflection
diffraction
4.1 Single-Slit Diffraction
diffraction grating
4.4 Diffraction Gratings
diffraction limit
4.5 Circular Apertures and Resolution
Diffused light
1.2 The Law of Reflection
diopters
2.5 The Eye
direction of polarization
1.7 Polarization
diverging lens
2.4 Thin Lenses
donor impurity
9.6 Semiconductors and Doping
double-slit interference experiment
6.6 Wave-Particle Duality
drift velocity
9.6 Semiconductors and Doping
E
Einstein
6.2 Photoelectric Effect
electric dipole transition
9.2 Molecular Spectra
electron affinity
9.1 Types of Molecular Bonds
electron configuration
8.4 The Exclusion Principle and the Periodic Table
electron microscopy
6.6 Wave-Particle Duality
electron number density
9.4 Free Electron Model of Metals
electroweak force
11.1 Introduction to Particle Physics
emission spectrum
6.4 Bohr’s Model of the Hydrogen Atom
emitter
6.1 Blackbody Radiation
endoscope
1.4 Total Internal Reflection
energy band
9.5 Band Theory of Solids
energy gap
9.5 Band Theory of Solids
energy levels
7.4 The Quantum Particle in a Box
energy of a photon
6.2 Photoelectric Effect
energy quantum number
7.4 The Quantum Particle in a Box
energy spectrum of hydrogen
6.4 Bohr’s Model of the Hydrogen Atom
energy-time uncertainty principle
7.2 The Heisenberg Uncertainty Principle
equilibrium separation distance
9.1 Types of Molecular Bonds
even function
7.1 Wave Functions
excited energy states of a hydrogen atom
6.4 Bohr’s Model of the Hydrogen Atom
expectation value
7.1 Wave Functions
F
face-centered cubic (FCC)
9.3 Bonding in Crystalline Solids
far point
2.5 The Eye
Farsightedness
2.5 The Eye
Fermi energy
9.4 Free Electron Model of Metals
Fermi factor
9.4 Free Electron Model of Metals
Fermi temperature
9.4 Free Electron Model of Metals
Feynman
11.5 The Standard Model
Feynman diagram
11.5 The Standard Model
Fiber optics
1.4 Total Internal Reflection
fine structure
8.3 Electron Spin
first focus
2.3 Images Formed by Refraction
first postulate
5.1 Invariance of Physical Laws
fission
10.5 Fission
Fizeau
1.1 The Propagation of Light
Fluorescence
8.5 Atomic Spectra and X-rays
focal length
2.2 Spherical Mirrors
focal plane
2.4 Thin Lenses
focal point
2.2 Spherical Mirrors
forward bias configuration
9.7 Semiconductor Devices
Foucault
1.1 The Propagation of Light
Fraunhofer
6.4 Bohr’s Model of the Hydrogen Atom
Fraunhofer lines
6.4 Bohr’s Model of the Hydrogen Atom
free electron model
9.4 Free Electron Model of Metals
Fresnel
Introduction
fringes
3.2 Mathematics of Interference
fundamental force
11.1 Introduction to Particle Physics
G
Gabor
4.7 Holography
Galilean relativity
5.1 Invariance of Physical Laws
Galilean transformation
5.5 The Lorentz Transformation
Galileo
2.8 Microscopes and Telescopes
gamma (
) rays
10.4 Nuclear Reactions
gamma decay
10.4 Nuclear Reactions
Gell-Mann
11.3 Quarks
geometric optics
1.1 The Propagation of Light
grand unified theory
11.1 Introduction to Particle Physics
ground state
8.1 The Hydrogen Atom
ground state energy
7.4 The Quantum Particle in a Box
ground state energy of the hydrogen atom
6.4 Bohr’s Model of the Hydrogen Atom
group velocity
6.5 De Broglie’s Matter Waves
H
Hahn
10.5 Fission
half-life
10.3 Radioactive Decay
Heisenberg
6.6 Wave-Particle Duality
Heisenberg’s uncertainty principle
7.2 The Heisenberg Uncertainty Principle
Hermite polynomial
7.5 The Quantum Harmonic Oscillator
high bandwidth
1.4 Total Internal Reflection
hologram
4.7 Holography
holography
4.7 Holography
horizontally polarized
1.7 Polarization
Hubble Space Telescope
4.5 Circular Apertures and Resolution
Hubble telescope
2.8 Microscopes and Telescopes
Hubble’s constant
11.6 The Big Bang
Hubble’s law
11.6 The Big Bang
Humphreys series
6.4 Bohr’s Model of the Hydrogen Atom
hybridization
9.1 Types of Molecular Bonds
Hydrogen-like ions
6.4 Bohr’s Model of the Hydrogen Atom
hyperfine structure
8.3 Electron Spin
hyperopia
2.5 The Eye
I
image distance
2.1 Images Formed by Plane Mirrors
image focus
2.3 Images Formed by Refraction
imaginary number
7.3 The Schrӧdinger Equation
impurity atom
9.6 Semiconductors and Doping
impurity band
9.6 Semiconductors and Doping
incoherent
3.1 Young's Double-Slit Interference
index of refraction
1.1 The Propagation of Light
inelastic scattering
6.3 The Compton Effect
inertial frame of reference
5.1 Invariance of Physical Laws
infinite square well
7.4 The Quantum Particle in a Box
interference fringes
3.1 Young's Double-Slit Interference
interferometer
3.5 The Michelson Interferometer
ionization energy
6.4 Bohr’s Model of the Hydrogen Atom
ionization limit of the hydrogen atom
6.4 Bohr’s Model of the Hydrogen Atom
iridescence
4.4 Diffraction Gratings
isotopes
10.1 Properties of Nuclei
J
junction transistor
9.7 Semiconductor Devices
K
Keck telescope
2.8 Microscopes and Telescopes
L
Large Hadron Collider (LHC)
11.4 Particle Accelerators and Detectors
laser
8.6 Lasers
law of reflection
1.2 The Law of Reflection
law of refraction
1.3 Refraction
Length contraction
5.4 Length Contraction
lens maker’s equation
2.4 Thin Lenses
lepton number
11.2 Particle Conservation Laws
lifetime
10.3 Radioactive Decay
light cone
5.5 The Lorentz Transformation
linear accelerator
11.4 Particle Accelerators and Detectors
linear magnification
2.2 Spherical Mirrors
liquid crystal displays (LCDs)
1.7 Polarization
liquid drop model
10.5 Fission
Lorentz factor
5.3 Time Dilation
Lorentz transformation
5.5 The Lorentz Transformation
Lyman series
6.4 Bohr’s Model of the Hydrogen Atom
M
Madelung constant
9.1 Types of Molecular Bonds
magnetic orbital quantum number
8.2 Orbital Magnetic Dipole Moment of the Electron
magnification
2.2 Spherical Mirrors
magnifying glass
2.7 The Simple Magnifier
majority carrier
9.6 Semiconductors and Doping
Malus’s law
1.7 Polarization
mass defect
10.2 Nuclear Binding Energy
mass number
10.1 Properties of Nuclei
Maxwell's equations
Introduction
metallic bonding
9.3 Bonding in Crystalline Solids
metastable state
8.6 Lasers
Michelson-Morley experiment
5.1 Invariance of Physical Laws
minority carrier
9.6 Semiconductors and Doping
mirror equation
2.2 Spherical Mirrors
missing order
4.3 Double-Slit Diffraction
momentum operator
7.1 Wave Functions
Moseley plot
8.5 Atomic Spectra and X-rays
Moseley’s law
8.5 Atomic Spectra and X-rays
muons
5.3 Time Dilation
myopia
2.5 The Eye
N
n-type semiconductor
9.6 Semiconductors and Doping
near point
2.5 The Eye
Nearsightedness
2.5 The Eye
net magnification
2.8 Microscopes and Telescopes
neutrino
10.4 Nuclear Reactions
neutron number
10.1 Properties of Nuclei
neutrons
10.1 Properties of Nuclei
Newton’s rings
3.4 Interference in Thin Films
Newtonian design
2.8 Microscopes and Telescopes
Newtonian mechanics
Introduction
nonreflective coatings
3.4 Interference in Thin Films
normalization
8.1 The Hydrogen Atom
normalization condition
7.1 Wave Functions
nuclear fusion
10.6 Nuclear Fusion
nuclear fusion reactor
10.6 Nuclear Fusion
nuclear model of the atom
6.4 Bohr’s Model of the Hydrogen Atom
nuclear reactor
10.5 Fission
nucleons
10.1 Properties of Nuclei
nuclide
10.1 Properties of Nuclei
O
object distance
2.1 Images Formed by Plane Mirrors
object focus
2.3 Images Formed by Refraction
odd function
7.1 Wave Functions
optical axis
2.2 Spherical Mirrors
optical power
2.5 The Eye
Optical stress analysis
1.7 Polarization
optically active
1.7 Polarization
orbital magnetic dipole moment
8.2 Orbital Magnetic Dipole Moment of the Electron
P
p-n junction
9.7 Semiconductor Devices
p-type semiconductor
9.6 Semiconductors and Doping
parent nucleus
10.4 Nuclear Reactions
particle accelerator
11.4 Particle Accelerators and Detectors
particle detector
11.4 Particle Accelerators and Detectors
Paschen series
6.4 Bohr’s Model of the Hydrogen Atom
Pauli’s exclusion principle
8.4 The Exclusion Principle and the Periodic Table,
11.1 Introduction to Particle Physics
periodic table
8.4 The Exclusion Principle and the Periodic Table
Pfund series
6.4 Bohr’s Model of the Hydrogen Atom
phasor diagram
4.2 Intensity in Single-Slit Diffraction
photocurrent
6.2 Photoelectric Effect
photoelectric effect
6.2 Photoelectric Effect
photoelectrode
6.2 Photoelectric Effect
photoelectrons
6.2 Photoelectric Effect
photon
6.2 Photoelectric Effect
Planck
6.1 Blackbody Radiation
Planck’s constant
6.1 Blackbody Radiation
Planck’s hypothesis of energy quanta
6.1 Blackbody Radiation
plane mirror
2.1 Images Formed by Plane Mirrors
Poisson’s spot
Introduction
polarized
1.7 Polarization
polyatomic molecule
9.1 Types of Molecular Bonds
population inversion
8.6 Lasers
position operator
7.1 Wave Functions
positron emission tomography (PET)
10.7 Medical Applications and Biological Effects of Nuclear Radiation
positrons
10.4 Nuclear Reactions
postulates of Bohr’s model
6.4 Bohr’s Model of the Hydrogen Atom
potential barrier
7.6 The Quantum Tunneling of Particles through Potential Barriers
power intensity
6.1 Blackbody Radiation
principal maxima
3.3 Multiple-Slit Interference
principal rays
2.2 Spherical Mirrors
probability density
7.1 Wave Functions
propagation vector
6.3 The Compton Effect
Proper length
5.4 Length Contraction
proper time
5.3 Time Dilation
proton-proton chain
10.6 Nuclear Fusion
protons
10.1 Properties of Nuclei
Q
Q value
10.6 Nuclear Fusion
quantized energies
6.1 Blackbody Radiation
quantum chromodynamics (QCD)
11.5 The Standard Model
quantum electrodynamics (QED)
11.5 The Standard Model
quantum phenomenon
6.2 Photoelectric Effect
quantum state of a Planck oscillator
6.1 Blackbody Radiation
quantum tunneling
7.6 The Quantum Tunneling of Particles through Potential Barriers
qubit
7.1 Wave Functions
R
radial probability density function
8.1 The Hydrogen Atom
radiation dose unit
10.7 Medical Applications and Biological Effects of Nuclear Radiation
radioactive dating
10.3 Radioactive Decay
radioactive decay
7.6 The Quantum Tunneling of Particles through Potential Barriers
radioactive decay law
10.3 Radioactive Decay
radioactivity
10.3 Radioactive Decay
radiopharmaceutical
10.7 Medical Applications and Biological Effects of Nuclear Radiation
radius of a nucleus
10.1 Properties of Nuclei
rainbow
1.5 Dispersion
ray model of light
1.1 The Propagation of Light
Rayleigh criterion
4.5 Circular Apertures and Resolution
Rayleigh–Jeans law
6.1 Blackbody Radiation
real image
2.1 Images Formed by Plane Mirrors
redshift
11.6 The Big Bang
reduced Planck’s constant
6.3 The Compton Effect
refraction
1.3 Refraction
relative biological effectiveness
10.7 Medical Applications and Biological Effects of Nuclear Radiation
Relativistic kinetic energy
5.9 Relativistic Energy
Relativistic momentum
5.8 Relativistic Momentum
relativistic velocity addition
5.6 Relativistic Velocity Transformation
repulsion constant
9.3 Bonding in Crystalline Solids
resolution
4.5 Circular Apertures and Resolution
resonant tunneling
7.6 The Quantum Tunneling of Particles through Potential Barriers
resonant-tunneling diode
7.6 The Quantum Tunneling of Particles through Potential Barriers
Rest energy
5.9 Relativistic Energy
rest frame
5.1 Invariance of Physical Laws
rest mass
5.8 Relativistic Momentum
retina
2.5 The Eye
reverse bias configuration
9.7 Semiconductor Devices
Rigel
6.1 Blackbody Radiation
Roemer
1.1 The Propagation of Light
roentgen equivalent man (rem)
10.7 Medical Applications and Biological Effects of Nuclear Radiation
rotational energy level
9.2 Molecular Spectra
Rutherford
6.4 Bohr’s Model of the Hydrogen Atom
Rutherford gold foil experiment
6.4 Bohr’s Model of the Hydrogen Atom
Rydberg constant for hydrogen
6.4 Bohr’s Model of the Hydrogen Atom
Rydberg formula
6.4 Bohr’s Model of the Hydrogen Atom
S
scanning electron microscope (SEM)
6.6 Wave-Particle Duality
scanning tunneling microscope (STM)
7.6 The Quantum Tunneling of Particles through Potential Barriers
scattering angle
6.3 The Compton Effect
Schrieffer
9.8 Superconductivity
Schrödinger
6.6 Wave-Particle Duality
Schrödinger’s cat
7.1 Wave Functions
Schrödinger’s equation
8.1 The Hydrogen Atom
Schrӧdinger’s time-dependent equation
7.3 The Schrӧdinger Equation
Schrӧdinger’s time-independent equation
7.3 The Schrӧdinger Equation
second focus
2.3 Images Formed by Refraction
second postulate of special relativity
5.1 Invariance of Physical Laws
secondary maximum
3.3 Multiple-Slit Interference
selection rule
9.2 Molecular Spectra
selection rules
8.5 Atomic Spectra and X-rays
semiconductor
9.5 Band Theory of Solids
sign conventions
2.4 Thin Lenses
simple cubic
9.3 Bonding in Crystalline Solids
simple magnifier
2.7 The Simple Magnifier
single-photon-emission CT (SPECT)
10.7 Medical Applications and Biological Effects of Nuclear Radiation
single-slit diffraction pattern
4.1 Single-Slit Diffraction
small-angle approximation
2.2 Spherical Mirrors
Snell
1.3 Refraction
Snell’s law
1.3 Refraction
soap bubble
3.4 Interference in Thin Films
space-time
5.5 The Lorentz Transformation
special theory of relativity
5.1 Invariance of Physical Laws
spectroscopic dispersion
4.4 Diffraction Gratings
spectroscopic notation
8.1 The Hydrogen Atom
spherical aberration
2.2 Spherical Mirrors
spin projection quantum number
8.3 Electron Spin
spin quantum number
8.3 Electron Spin
spin-flip transitions
8.3 Electron Spin
spin-orbit coupling
8.3 Electron Spin
Standard Model
11.5 The Standard Model
standing wave state
7.4 The Quantum Particle in a Box
state reduction
7.1 Wave Functions
stationary state
7.4 The Quantum Particle in a Box
Stefan–Boltzmann constant
6.1 Blackbody Radiation
Stefan’s law
6.1 Blackbody Radiation
Stern-Gerlach experiment
8.3 Electron Spin
stimulated emission
8.6 Lasers
stopping potential
6.2 Photoelectric Effect
strangeness
11.2 Particle Conservation Laws
Strassman
10.5 Fission
synchrotron
11.4 Particle Accelerators and Detectors
synchrotron radiation
11.4 Particle Accelerators and Detectors
T
theory of everything
11.1 Introduction to Particle Physics
thin lenses
2.4 Thin Lenses
thin-film interference
3.4 Interference in Thin Films
thin-lens approximation
2.4 Thin Lenses
thin-lens equation
2.4 Thin Lenses
thought experiment
5.2 Relativity of Simultaneity
Time dilation
5.3 Time Dilation
time-modulation factor
7.3 The Schrӧdinger Equation
Tonomura
6.6 Wave-Particle Duality
Total energy
5.9 Relativistic Energy
total internal reflection
1.4 Total Internal Reflection
transition metal
8.4 The Exclusion Principle and the Periodic Table
transmission electron microscope (TEM)
6.6 Wave-Particle Duality
transmission probability
7.6 The Quantum Tunneling of Particles through Potential Barriers
transuranic element
10.4 Nuclear Reactions
tritium
10.1 Properties of Nuclei
tunneling probability
7.6 The Quantum Tunneling of Particles through Potential Barriers
two-slit interference
7.1 Wave Functions
type I superconductor
9.8 Superconductivity
type II superconductor
9.8 Superconductivity
V
valence band
9.5 Band Theory of Solids
valence electron
8.4 The Exclusion Principle and the Periodic Table
Van de Graaff accelerator
11.4 Particle Accelerators and Detectors
van der Waals bond
9.1 Types of Molecular Bonds
vertex
2.2 Spherical Mirrors
vertically polarized
1.7 Polarization
vibrational energy level
9.2 Molecular Spectra
virtual image
2.1 Images Formed by Plane Mirrors
virtual particle
11.5 The Standard Model
von Laue
4.6 X-Ray Diffraction
W
W and Z boson
11.1 Introduction to Particle Physics
wave function
7.1 Wave Functions
wave function collapse
7.1 Wave Functions
wave number
6.3 The Compton Effect
wave quantum mechanics
6.5 De Broglie’s Matter Waves
wave-particle duality
6.6 Wave-Particle Duality
weak nuclear force
11.1 Introduction to Particle Physics
Wheeler
10.5 Fission
width of the central peak
4.2 Intensity in Single-Slit Diffraction
Wien’s displacement law
6.1 Blackbody Radiation
Wilkinson Microwave Anisotropy Probe (WMAP)
11.7 Evolution of the Early Universe
work function
6.2 Photoelectric Effect
world line
5.5 The Lorentz Transformation
X
X-ray diffraction
4.6 X-Ray Diffraction
Z
Zeeman effect
8.2 Orbital Magnetic Dipole Moment of the Electron