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                            Municipal Liceum  57

       Laws, rules, principles, effects, paradoxes, limits, constants,
               experiments, & thought-experiments in physics.

                                                     Pupil : Morozov Michael

Ampere's law (A.M. Ampere)
     The  line  integral  of  the  magnetic  flux  around  a  closed   curve
isproportional to the algebraic  sum  of  electric  currents  flowingthrough
that closed curve.    This was later modified to add a second term  when  it
wasincorporated into Maxwell's equations.
Anthropic principle
     Weak  anthropic  principle.    The   conditions   necessary   for   the
development of intelligent life will be met only in certain    regions  that
are limited in space and time.  That is, the    region of  the  Universe  in
which we live is not necessarily    representative of a  purely  random  set
of initial conditions;    only those favorable  to  intelligent  life  would
actually    develop creatures who wonder  what  the  initial  conditions  of
the Universe were.
    Strong anthropic principle.  A more forceful argument that  the     weak
principle:  It states, rather straightforwardly, that if    the laws of  the
Universe were not conducive to the development of intelligent  creatures  to
ask about the initial conditions    of the Universe, intelligent life  would
never have evolved to    ask the question in  the  first  place.   In  other
words, the laws    of the Universe are the way  they  are  because  if  they
weren't,    you would not be able to ask such a question.
Arago spot (D.F.J. Arago)
    A bright spot that appears in the shadow of a uniform disc  beingbacklit
by monochromatic light emanating from a point source.
Archimedes' principle
    A body that is submerged in a fluid is buoyed  up  by  a  force  equalin
magnitude to the weight of the fluid that is displaced,  anddirected  upward
along a line through the center of gravity of thedisplaced fluid.
Atwood's machine
    A weight-and-pulley system devised to  measure  the  acceleration  dueto
gravity at Earth's surface by measuring the  net  acceleration  ofa  set  of
weights of known mass around a frictionless pulley.
Avogadro constant; L; NA (Count A. Avogadro; 1811)
    The number of atoms or molecules in a sample of an idea gas  whichis  at
standard temperature and pressure.  It is equal to about 6.022 52.1023  mol-
Avogadro's hypothesis (Count A. Avogadro; 1811)
    Equal volumes of all gases at the same temperature  and  pressurecontain
equal numbers of molecules.  It is, in fact, only true forideal gases.
Balmer series (J. Balmer; 1885)
    An equation which describes the emission  spectrum  of  hydrogen  whenan
electron is jumping to the second orbital;  four  of  the  linesare  in  the
visible spectrum, and the remainder are in theultraviolet.
Baryon decay
    The theory, predicted by several grand-unified theories, that aclass  of
subatomic particles called baryons (of  which  the  nucleons--  protons  and
neutrons  --  are  members)  are  not  ultimately  stablebut  indeed  decay.
Present theory and experimentation demonstratethat  if  protons  are  indeed
unstable, they decay with a halflife ofat least 1034 y.
Bernoulli's equation
    An equation which states that an  irrotational  fluid  flowingthrough  a
pipe flows at a rate which is inversely proportional  tothe  cross-sectional
area of the pipe.  That is, if the pipeconstricts, the fluid  flows  faster;
if it widens, the fluid flowsslower.
BCS theory (J. Bardeen, L.N. Cooper, J.R. Schrieffer; 1957)
    A theory put forth to explain both  superconductivity  andsuperfluidity.
It suggests that in the superconducting (orsuperfluid) state electrons  form
Cooper pairs, where two electronsact as a single unit.  It takes  a  nonzero
amount  of  energy  tobreak  such  pairs,  and  the  imperfections  in   the
superconductingsolid  (which  would  normally  lead   to   resistance)   are
incapable ofbreaking the pairs,  so  no  dissipation  occurs  and  there  is

Biot-Savart law (J.B. Biot, F. Savart)
    A  law  which  describes  the  contributions  to  a  magnetic  field  by
anelectric current.  It is analogous to Coulomb's law forelectrostatics.
Blackbody radiation
    The radiation -- the radiance at particular  frequencies  all  acrossthe
spectrum -- produced by a blackbody  --  that  is,  a  perfectradiator  (and
absorber) of heat.  Physicists  had  difficultyexplaining  it  until  Planck
introduced his quantum of action.
Bode's law
    A mathematical formula which generates, with a fair  amount  ofaccuracy,
the semimajor axes of the planets in order out from theSun.  Write down  the
sequence 0, 3, 6, 12, 24, . . . and then add4 to  each  term.   Then  divide
each term by 10.  This is intended togive you the positions of  the  planets
measured in astronomicalunits.
     Bode's   law   had   no   theoretical   justification   when   it   was
firstintroduced;   it   did,   however,   agree   with    the    soon-to-be-
discoveredplanet    Uranus'    orbit    (19.2    au    actual;    19.7    au
predicted).Similarly,  it  predicted  a  missing  planet  betwen  Mars   and
Jupiter,and  shortly  thereafter  the   asteroids   were   found   in   very
similarorbits (2.8  au  actual  for  Ceres;  2.8  au  predicted).   However,
theseries seems to skip over Neptune's orbit.
Bohr magneton (N. Bohr)
    The quantum of magnetic moment.
Bohr radius (N. Bohr)
    The distance corresponding the mean  distance  of  an  electron  fromthe
nucleus in the ground state.
Boltzmann constant; k (L. Boltzmann)
    A constant  which  describes  the  relationship  between  temperatureand
kinetic energy for molecules in an ideal gas.  It is equal to1.

Boyle's law (R. Boyle; 1662); Mariotte's law (E. Mariotte; 1676)
    The product of the pressure and the volume of an  ideal  gas  atconstant
temperature is a constant.
Brackett series (Brackett)
    The series which describes the emission  spectrum  of  hydrogen  whenthe
electron is jumping to the fourth orbital.   All  of  the  linesare  in  the
infrared portion of the spectrum.
Bragg's law (Sir W.L. Bragg; 1912)
    When a beam of x-rays strikes a crystal surface in  which  thelayers  of
atoms  or  ions  are  regularly  separated,  the  maximumintensity  of   the
reflected ray occurs  when  the  sine  of  thecompliment  of  the  angle  of
incidence is equal to an  integermultiplied  by  the  wavelength  of  x-rays
divided by twice thedistance between layers of atoms or ions.
Brewster's law (D. Brewster)
    The extent of the polarization  of  light  reflected  from  atransparent
surface is a maximum when  the  reflected  ray  is  atright  angles  to  the
refracted ray.
Brownian motion (R. Brown; 1827)
     The  continuous  random   motion   of   solid   microscopic   particles
whensuspended   in   a   fluid   medium   due   to   the   consequence    of
continuousbombardment by atoms and molecules.
Carnot's theorem (S. Carnot)
     The  theorem  which   states   that   no   engine   operating   between
twotemperatures can be more efficient than a reversible engine.
centrifugal pseudoforce
    A pseudoforce -- a fictitious force  resulting  from  being  in  a  non-
inertial frame of reference -- that occurs  when  one  is  moving  inuniform
circular motion.  One feels a "force" outward from thecenter of motion.
Chandrasekhar limit (S. Chandrasekhar; 1930)
    A limit which mandates  that  no  white  dwarf  (a  collapsed,degenerate
star) can be more massive than about 1.2 solar masses.Anything more  massive
must inevitably collapse into a neutronstar.
Charles' law (J.A.C. Charles; c. 1787)
    The volume of an ideal gas at constant pressure  is  proportional  tothe
thermodynamic temperature of that gas.
Cherenkov radiation (P.A. Cherenkov)
    Radiation emitted by a  massive  particle  which  is  moving  fasterthan
light in the medium through which it is travelling.  Noparticle  can  travel
faster than light in vacuum, but the speed oflight in other media,  such  as
water, glass, etc.,  are  considerablylower.   Cherenkov  radiation  is  the
electromagnetic analogue of thesonic boom, though Cherenkov radiation  is  a
shockwave set up inthe electromagnetic field.
Complementarity principle (N. Bohr)
    The principle that a given system cannot exhibit both  wave-likebehavior
and particle-like behavior at the same time.   That  is,certain  experiments
will reveal the wave-like nature of a system,and  certain  experiments  will
reveal the particle-like nature of asystem, but no  experiment  will  reveal
both simultaneously.
Compton effect (A.H. Compton; 1923)
    An effect that demonstrates that photons (the quantum  ofelectromagnetic
radiation) have momentum.  A photon fired at astationary particle,  such  as
an electron, will impart momentum tothe electron and, since its  energy  has
been decreased, willexperience a corresponding decrease in frequency.
Coriolis pseudoforce (G. de Coriolis; 1835)
    A pseudoforce -- a fictitious  force,  like  the  centrifugal  "force"--
which  arises  because  the  rotation  of  the  Earth   varies   atdifferent
latitutdes (maximum at the equator, zero at the poles).
correspondence principle.
    The principle that when a new, more specialized theory is  putforth,  it
must reduce to the more general (and  usually  simpler)theory  under  normal
circumstances.  There are correspondenceprinciples  for  general  relativity
to special relativity andspecial relativity to Newtonian mechanics, but  the
most widelyknown correspondence  principle  (and  generally  what  is  meant
whenone says "correspondence principle")  is  that  of  quantum  mechanicsto
classical mechanics.
Cosmic background radiation; primal glow
    The background of radiation mostly in  the  frequency  range  3.1011  to
3.108  Hz  discovered  in  space  in  1965.   It  is   believedto   be   the
cosmologically  redshifted  radiation  released  by  the   BigBang   itself.
Presently it has an energy density in empty space ofabout
Cosmological redshift
    An effect where light emitted from a  distant  source  appearsredshifted
because of the expansion of space itself.  Compare withthe Doppler effect.
Coulomb's law
     The  primary  law  for  electrostatics,  analogous  to   Newton's   law
ofuniversal gravitation.  It states that the force between two  pointcharges
is proportional to the algebraic product of theirrespective charges as  well
as proportional to the inverse squareof the distance between them.
CPT theorem
Curie-Weiss law (P. Curie, P.-E. Weiss)
    A more general form of Curie's law, which states that  thesusceptibility
of a paramagnetic substance is inverselyproportional  to  the  thermodynamic
temperature of the substanceless the Weiss  constant,  a  characteristic  of
that substance.
Curie's law (P. Curie)
    The susceptibility of a paramagnetic substance is  inverselyproportional
to  the  thermodynamic  temperature  of  the   substance.The   constant   of
proportionality is called the Curie constant.
Dalton's law of partial pressures (J. Dalton)
    The total pressure of a mixture of ideal gases is  equal  to  the  sumof
the partial pressures of its components; that is, the  sum  ofthe  pressures
that each component would exert if it  were  presentalone  and  occuped  the
same volume as the mixture.

Davisson-Germer experiment (C.J. Davisson, L.H. Germer; 1927)
    An experiment that conclusively confirmed the wave  nature  ofelectrons;
diffraction patterns were observed by an  electron  beampenetrating  into  a
nickel target.
De Broglie wavelength (L. de Broglie; 1924)
    The prediction that particles also have wave  characteristics,where  the
effective wavelength of a particle would  be  inverselyproportional  to  its
momentum, where the constant ofproportionality is the Planck constant.
Doppler effect (C.J. Doppler)
    Waves emitted by a moving observer will  be  blueshifted(compressed)  if
approaching, redshifted (elongated) if receding.It occurs both in  sound  as
well as electromagnetic phenomena,although it takes on  different  forms  in
Dulong-Petit law (P. Dulong, A.T. Petit; 1819)
    The molar heat capacity is approximately equal  to  the  three  timesthe
gas constant.
Einstein-Podolsky-Rosen effect
    Consider the  following  quantum  mechanical  thought-experiment:Take  a
particle which is at rest and has spin zero.   Itspontaneously  decays  into
two fermions (spin 0.5 particles), whichstream away in  opposite  directions
at high speed.  Due to the lawof conservation of spin, we know that  one  is
a spin +0.5  and theother is spin -0.5.  Which one is which?   According  to
quantummechanics,  neither  takes  on  a  definite   state   until   it   is
observed(the wavefunction is collapsed).
    The EPR effect demonstrates that if one  of  the  particles  isdetected,
and its spin is then measured, then the other particle-- no matter where  it
is in the Universe -- instantaneously isforced to choose as  well  and  take
on the role of the otherparticle.  This illustrates that  certain  kinds  of
quantuminformation travel instantaneously; not everything is  limited  bythe
speed of light.
    However, it can be easily demonstrated that  this  effect  doesnot  make
faster-than-light communication possible.
Equivalence principle
    The basic postulate of A. Einstein's general theory of  relativity,which
posits  that  an  acceleration  is  fundamentallyindistinguishable  from   a
gravitational field.  In other words, ifyou are  in  an  elevator  which  is
utterly sealed and protected fromthe  outside,  so  that  you  cannot  "peek
outside," then if you feel aforce (weight), it is  fundamentally  impossible
for you to saywhether the elevator is  present  in  a  gravitational  field,
orwhether the  elevator  has  rockets  attached  to  it  and  isaccelerating
     The  equivalence  principle  predicts  interesting  generalrelativistic
effects because not only are the twoindistinguishable  to  human  observers,
but also to the Universe aswell, in a way -- any  effect  that  takes  place
when an observer isaccelerating should also take place  in  a  gravitational
field, andvice versa.
    The region around a rotating black hole, between  the  event  horizonand
the static limit, where rotational energy can  be  extractedfrom  the  black
Event horizon
    The radius of surrounding a black hole at which a particle wouldneed  an
escape velocity of lightspeed to escape; that is, thepoint of no return  for
a black hole.
Faraday constant; F (M. Faraday)
    The electric charge carried by one mole of electrons (or  singly-ionized
ions).  It  is  equal  to  the  product  of  the  Avogadroconstant  and  the
(absolute value of the) charge on an electron; itis
9.648670.104 C/mol.
Faraday's law (M. Faraday)
     The  line  integral  of  the  electric  flux  around  a  closed   curve
isproportional to the instantaneous time rate of change of themagnetic  flux
through a surface bounded by that closed curve.
Faraday's laws of electrolysis (M. Faraday)
  1. The amount of chemical change during electrolysis  is     proportional
     to the charge passed.
   2.  The charge required to deposit or liberate a mass is     proportional
   to the charge of the ion, the mass, and    inversely proprtional  to  the
   relative ionic mass.  The    constant of proportionality is  the  Faraday
Faraday's laws of electromagnetic induction (M. Faraday)
  1. An electromotive force is induced in a conductor when the     magnetic
     field surrounding it changes.
  2. The magnitude of the electromotive force  is  proportional  to     the
     rate of change of the field.
   3.   The  sense  of  the  induced  electromotive  force  depends  on  the
   direction of the rate of the change of the field.
Fermat's principle; principle of least time (P. de Fermat)
    The principle, put forth by P. de Fermat, states that the  pathtaken  by
a ray of light between any two points in a system  isalways  the  path  that
takes the least time.
Fermi paradox
    E. Fermi's conjecture, simplified  with  the  phrase,  "Where  arethey?"
questioning that if the Galaxy is filled with  intelligentand  technological
civilizations, why haven't they come to us yet?There  are  several  possible
answers to this question, but since weonly have the vaguest  idea  what  the
right conditions for life andintelligence in  our  Galaxy,  it  and  Fermi's
paradox are no morethan speculation.
Gauss' law (K.F. Gauss)
     The  electric  flux  through  a  closed  surface  is  proportional   to
thealgebraic sum of electric charges contained within that closedsurface.
Gauss' law for magnetic fields (K.F. Gauss)
    The magnetic flux through a closed surface is zero;  no  magneticcharges
Grandfather paradox
    A paradox proposed to discount  time  travel  and  show  why  itviolates
causality.   Say  that  your  grandfather  builds  a  timemachine.   In  the
present, you use his time machine to go back  intime  a  few  decades  to  a
point before he married his wife (yourgrandmother).  You meet  him  to  talk
about things, and an argumentensues  (presumably  he  doesn't  believe  that
you're hisgrandson/granddaughter), and you accidentally kill him.
    If he died before he met your grandmother and  never  hadchildren,  then
your parents could certainly never have met (one ofthem didn't  exist!)  and
could never have given birth to you.   Inaddition,  if  he  didn't  live  to
build his time machine, what areyou doing here in the past alive and with  a
time machine, if youwere never born and it was never built?
Hall effect
    When charged particles flow through a tube  which  has  both  anelectric
field and a magnetic field (perpendicular to the electricfield)  present  in
it, only certain velocities of the chargedparticles are preferred, and  will
make it undeviated through thetube; the rest  will  be  deflected  into  the
sides.  This effect isexploited in such devices  as  the  mass  spectrometer
and in theThompson experiment.  This is called the Hall effect.
Hawking radiation (S.W. Hawking; 1973)
    The theory that black holes  emit  radiation  like  any  other  hotbody.
Virtual  particle-antiparticle  pairs   are   constantly   beingcreated   in
supposedly empty space.  Every once in a while, onewill be  created  in  the
vicinity of a black hole's event horizon.One of  these  particles  might  be
catpured by the black hole,forever trapped, while  the  other  might  escape
the black hole'sgravity.  The trapped particle, which  would  have  negative
energy(by definition),  would  reduce  the  mass  of  the  black  hole,  and
theparticle which escaped would have positive energy.  Thus, from  adistant,
one would see the black  hole's  mass  decrease  and  aparticle  escape  the
vicinity; it would appear as if the black holewere emitting radiation.   The
rate of emission has a negativerelationship  with  the  mass  of  the  black
hole; massive black holesemit radiation  relatively  slowly,  while  smaller
black holes emitradiation -- and thus decrease their mass -- more rapidly.

Heisenberg uncertainty principle (W. Heisenberg; 1927)
     A  principle,  central  to  quantum  mechanics,   which   states   that
themomentum (mass times velocity) and the position of a particlecannot  both
be known to infinite accuracy; the more you  know  aboutone,  the  lest  you
know about the other.
    It can  be  illustrated  in  a  fairly  clear  way  as  follows:   Tosee
something (let's say an electron), we have to fire  photons  atit,  so  they
bounce off and come back to us, so  we  can  "see"  it.If  you  choose  low-
frequency photons, with a low energy, they donot  impart  much  momentum  to
the electron, but they give you a veryfuzzy picture, so you  have  a  higher
uncertainty in position sothat you can have a higher certainty in  momentum.
 On the otherhand, if you were to  fire  very  high-energy  photons  (x-rays
orgammas) at the electron, they would give you a very clear pictureof  where
the electron is (high certainty in position), but wouldimpart a  great  deal
of momentum to the electron (higheruncertainty in momentum).     In  a  more
generalized sense,  the  uncertainty  principle  tellsus  that  the  act  of
observing changes the observed in fundamentalway.
Hooke's law (R. Hooke)
     The  stress  applied  to  any  solid  is  proportional  to  the  strain
itproduces within the elastic limit for that  solid.   The  constant  ofthat
proportionality is the Young modulus of elasticity for thatsubstance.
Hubble constant; H0 (E.P. Hubble; 1925)
    The constant which determines the relationship between thedistance to  a
galaxy and its velocity of recession due to theexpansion  of  the  Universe.
It is not known to great accuracy, butis believed to lie between 49 and 95
Hubble's law (E.P. Hubble; 1925)
    A relationship  discovered  between  distance  and  radial  velocity.The
further away a galaxy is away from is, the faster it  isreceding  away  from
us.  The constant of proportionality isHubble's constant, H0.  The cause  is
interpreted as the expansionof space itself.
Huygens' construction; Huygens' principle (C. Huygens)
    The mechanics propagation of a wave of light  is  equivalent  toassuming
that every point on the wavefront acts as point source ofwave emission.
Ideal gas constant; universal molar gas constant; R
    The constant that appears in the ideal  gas  equation.   It  is  equalto
8.314 34.
Ideal gas equation
    An equation which sums up the ideal gas laws in one simpleequation.   It
states that the product of the pressure and thevolume of a sample  of  ideal
gas is equal to the product of theamount of gas present, the temperature  of
the sample, and theideal gas constant.
Ideal gas laws
    Boyle's law.  The pressure of an ideal gas is inversely proportional  to
the volume of the gas at constant temperature.
    Charles' law.  The volume of an ideal gas is  directly  proportional  to
the thermodynamic temperature at constant pressure.
     The  pressure  law.   The  pressure  of  an  ideal  gas   is   directly
proportional to the thermodynamic temperature at constant volume.
Joule-Thomson effect; Joule-Kelvin effect (J. Joule, W. Thomson)
    The change in temperature that occurs when a gas  expands  into  aregion
of lower pressure.
Joule's laws
    Joule's first law.  The heat produced when  an  electric  current  flows
through a resistance for a specified time is equal  to  the  square  of  the
current multiplied by the resistivity multiplied by the time.
    Joule's second law.  The internal energy of an ideal gas is  independent
of its volume and pressure, depending only on its temperature.
Josephson effects (B.D. Josephson; 1962)
     Electrical  effects  observed  when   two   superconducting   materials
areseparated by a thin layer of insulating material.

Kepler's laws (J. Kepler)
    Kepler's first law.  A planet orbits the Sun in an ellipse with the  Sun
at one focus.
   Kepler's second law.  A ray directed from the Sun to a planet sweeps  out
equal areas in equal times.
    Kepler's third law.  The square of the period of  a  planet's  orbit  is
proportional to the cube of that planet's semimajor axis;  the  constant  of
proportionality is the same for all planets.
Kerr effect (J. Kerr; 1875)
    The ability of certain  substances  to  differently  refract  lightwaves
whose vibrations are in different directions when thesubstance is placed  in
an electric field.
Kirchhoff's law of radiation (G.R. Kirchhoff)
     The  emissivity  of  a  body  is  equal  to  its  absorptance  at   the
Kirchhoff's rules (G.R. Kirchhoff)
    The loop rule.  The sum of the potential differences  encountered  in  a
round trip around any closed loop in a circuit is zero.
    The point rule.  The sum of the currents toward a branch point is  equal
to the sum of the currents away from the same branch point.
Kohlrausch's law (F. Kohlrausch)
    If a salt is dissolved in water, the conductivity of the solutionis  the
sum of two values -- one depending on the positive ions andthe other on  the
negative ions.
Lambert's laws (J.H. Lambert)
    Lambert's first law.  The illuminance on a surface illuminated by  light
falling on it perpendicularly from a point source  is  proportional  to  the
inverse square of the distance between the surface and the source.
    Lambert's second law.  If the rays meet the surface at  an  angle,  then
the illuminance is also proportional to the cosine of  the  angle  with  the
     Lambert's  third  law.   The  luminous  intensity  of  light  decreases
exponentially with  the  distance  that  it  travels  through  an  absorbing
Landauer's principle
    A  principle  which  states  that  it  doesn't  explicitly  take  energy
tocompute data, but rather it takes energy to erase any  data,since  erasure
is an important step in computation.
Laplace's equation (P. Laplace)
      For   steady-state   heat   conduction   in   one    dimension,    the
temperaturedistribution  is  the  solution  to  Laplace's  equation,   which
statesthat the second derivative of temperature with respect  todisplacement
is zero.
Laue pattern (M. von Laue)
      The   pattern   produced   on   a   photographic   film   when   high-
frequencyelectromagnetic  waves  (such   as   x-rays)   are   fired   at   a
Laws of conservation
    A law which  states  that,  in  a  closed  system,  the  total  quantity
ofsomething will not increase or decrease, but remain exactly thesame.   For
physical quantities, it states that  something  canneither  be  created  nor
    The most commonly seen are  the  laws  of  conservation  of  mass-energy
(formerly two conservation laws before A. Einstein), ofelectric  charge,  of
linear momentum, and of angular momentum.There are several others that  deal
more with  particle  physics,such  as  conservation  of  baryon  number,  of
strangeness, etc., whichare conserved in some fundamental  interactions  but
not others.
Law of reflection
     For  a  wavefront  intersecting  a  reflecting   surface,   the   angle
ofincidence is equal to the angle of reflection.
Laws of black hole dynamics
    First law of black hole dynamics.  For interactions between black  holes
and normal matter, the conservation laws of total  energy,  total  momentum,
angular momentum, and electric charge,    hold.
    Second law of black hole dynamics.  With  black  hole  interactions,  or
interactions between black holes and normal matter, the sum of  the  surface
areas of all black holes involved can never decrease.
Laws of thermodynamics
    First law of thermodynamics.  The change in internal energy of a  system
is the sum of the heat transferred to or from the system and the  work  done
on or by the system.
    Second  law  of  thermodynamics.   The  entropy  --  a  measure  of  the
unavailability of a system's energy to do useful work -- of a closed  system
tends to increase with time.
    Third  law  of  thermodynamics.   For  changes  involving  only  perfect
crystalline solids at absolute zero, the change  of  the  total  entropy  is
    Zeroth law of  thermodynamics.   If  two  bodies  are  each  in  thermal
equilibrium with a  third  body,  then  all  three  bodies  are  in  thermal
equilibrium with each other.
Lawson criterion (J.D. Lawson)
    A condition for the release of energy from a  thermonuclearreactor.   It
is usually stated as the minimum value for theproduct of the density of  the
fuel particles and the containmenttime for energy breakeven.   For  a  half-
and-half mixture ofdeuterium and tritium at ignition temperature,  nG  t  is
between1014 and 1015 s/cm3.
Le Chatelier's principle (H. Le Chatelier; 1888)
    If a system is in equilibrium, then  any  change  imposed  on  thesystem
tends to shift the equilibrium to reduce the effect of thatapplied change.
Lenz's law (H.F. Lenz; 1835)
    An induced electric current always flows  in  such  a  direction  thatit
opposes the change producing it.
Loschmidt constant; Loschmidt number; NL
    The number of particles per unit  volume  of  an  ideal  gas  atstandard
temperature and pressure.  It has the value 2.68719.1025 m-3.
Lumeniferous aether
    A substance, which filled all the empty spaces between matter,which  was
used to  explain  what  medium  light  was  "waving"  in.   Nowit  has  been
discredited, as Maxwell's equations imply thatelectromagnetic radiation  can
propagate in a vacuum, since theyare  disturbances  in  the  electromagnetic
field rather thantraditional waves in some substance, such as water waves.
Lyman series
     The  series  which  describes  the  emission   spectrum   of   hydrogen
whenelectrons are jumping to the ground state.  All of the lines  arein  the
Mach's principle (E. Mach; 1870s)
     The  inertia  of  any  particular  particle  or  particles  of   matter
isattributable to the interaction between that piece of matter  andthe  rest
of the Universe.  Thus, a body in isolation would have noinertia.
Magnus effect
    A rotating cylinder in a moving fluid  drags  some  of  the  fluidaround
with it, in its direction of rotation.   This  increases  thespeed  in  that
region, and thus the pressure is lower.Consequently, there is  a  net  force
on the cylinder in thatdirection, perpendicular to the flow  of  the  fluid.
This is calledthe Magnus effect.
Malus's law (E.L. Malus)
    The light intensity travelling through  a  polarizer  is  proportionalto
the initial intensity of the light and the square of the cosineof the  angle
between the polarization of the light ray and thepolarization  axis  of  the
Maxwell's demon (J.C. Maxwell)
    A thought experiment illustrating the concepts  of  entropy.   Wehave  a
container of gas which is partitioned into two equal sides;each side  is  in
thermal equilibrium with the other.  The walls(and  the  partition)  of  the
container are a perfect insulator.    Now imagine  there  is  a  very  small
demon who is waiting at thepartition next to a  small  trap  door.   He  can
open and close thedoor with negligible work.  Let's say he  opens  the  door
to allow afast-moving molecule to travel from the left side  to  the  right,
orfor a slow-moving molecule to travel from the right side to the left,  and
keeps it closed for all other molecules.  The net effectwould be a  flow  of
heat -- from the left side to the right -- eventhough the container  was  in
thermal equilibrium.  This is  clearlya  violation  of  the  second  law  of
thermodynamics.    So where did we go wrong?  It turns out that  information
hasto do with entropy as well.  In order to sort out the  moleculesaccording
to speeds, the demon would be having to keep  a  memory  ofthem  --  and  it
turns out that increase in entropy of the simplemaintenance of  this  simple
memory would more than make up for thedecrease in entropy due  to  the  heat
Maxwell's equations (J.C. Maxwell; 1864)
    Four elegant equations which describe classical  electromagnetismin  all
its splendor.  They are:
    Gauss' law.  The electric flux through a closed surface is  proportional
to the algebraic sum  of  electric  charges  contained  within  that  closed
    Gauss' law for magnetic fields.  The  magnetic  flux  through  a  closed
surface is zero; no magnetic charges exist.
    Faraday's law.  The line integral of the electric flux around  a  closed
curve is proportional to the  instantaneous  time  rate  of  change  of  the
magnetic flux through a surface bounded by that closed curve.
    Ampere's law, modified form.  The line integral  of  the  magnetic  flux
around a closed curve is proportional to the sum of two terms:   first,  the
algebraic sum of electric currents flowing through that  closed  curve;  and
second, the instantaneous time rate of change of the electric  flux  through
a surface bounded by that closed curve.
    In addition to describing electromagnetism,  his  equations  alsopredict
that waves can propagate through the electromagneticfield, and would  always
propagate at the same speed -- these are electromagnetic waves.
Meissner effect (W. Meissner; 1933)
    The decrease of the magnetic flux within a superconducting metalwhen  it
is  cooled  below  the  critical   temperature.    That   is,superconducting
materials reflect magnetic fields.
Michelson-Morley experiment (A.A. Michelson, E.W. Morley; 1887)
    Possibly the most famous null-experiment of all time, designed  toverify
the existence of  the  proposed  "lumeniferous  aether"  throughwhich  light
waves were thought to propagate.  Since the Earthmoves through this  aether,
a lightbeam fired in the Earth'sdirection of motion  would  lag  behind  one
fired sideways, where noaether effect would  be  present.   This  difference
could be detectedwith the use of an interferometer.
    The experiment showed absolutely no aether  shift  whatsoever,where  one
should have been quite detectable.  Thus the aetherconcept  was  discredited
as was the constancy of the speed oflight.
Millikan oil drop experiment (R.A. Millikan)
    A famous experiment designed to measure the electronic  charge.Drops  of
oil were carried  past  a  uniform  electric  field  betweencharged  plates.
After charging the drop with x-rays, he adjustedthe electric  field  between
the plates so that the oil drop wasexactly balanced  against  the  force  of
gravity.  Then the charge onthe drop would  be  known.   Millikan  did  this
repeatedly and foundthat  all  the  charges  he  measured  came  in  integer
multiples only ofa certain smallest  value,  which  is  the  charge  on  the
Newton's law of universal gravitation (Sir I. Newton)
     Two  bodies  attract  each  other  with  equal  and  opposite   forces;
themagnitude of this force is proportional to the product of  the  twomasses
and is also proportional to the inverse square of  thedistance  between  the
centers of mass of the two bodies.
Newton's laws of motion (Sir I. Newton)
    Newton's first law of motion.  A body continues in its state of rest  or
of uniform motion unless it is acted upon by an external force.
    Newton's second law of motion.  For an  unbalanced  force  acting  on  a
body, the acceleration produces is proportional to the force impressed;  the
constant of proportionality is the inertial mass of the body.
    Newton's third law of motion.  In a system where no external forces  are
present, every action is always opposed by an equal and opposite reaction.
Ohm's law (G. Ohm; 1827)
    The ratio of the potential difference between the ends of aconductor  to
the current flowing through it is constant; theconstant  of  proportionality
is called the resistance, and isdifferent for different materials.
Olbers' paradox (H. Olbers; 1826)
    If the Universe is infinite, uniform, and unchanging then theentire  sky
at night would be bright -- about as  bright  as  the  Sun.The  further  you
looked out into space, the  more  stars  there  wouldbe,  and  thus  in  any
direction in which you looked your line-of-sight  would  eventually  impinge
upon a star.  The paradox isresolved by the  Big  Bang  theory,  which  puts
forth that theUniverse is not infinite, non-uniform, and changing.
Pascal's principle
     Pressure  applied  to   an   enclosed   imcompressible   static   fluid
istransmitted undiminished to all parts of the fluid.
Paschen series
    The series which describes the emission  spectrum  of  hydrogen  whenthe
electron is jumping to the third  orbital.   All  of  the  linesare  in  the
infrared portion of the spectrum.
Pauli exclusion principle (W. Pauli; 1925)
    No two identical fermions in a system, such as electrons in anatom,  can
have an identical set of quantum numbers.
Peltier effect (J.C.A. Peltier; 1834)
    The change in temperature produced at a junction  between  twodissimilar
metals  or  semiconductors  when  an  electric  currentpasses  through   the
permeability of free space; magnetic constant; m 0
    The ratio of the magnetic flux density in  a  substance  to  theexternal
field strength for vacuum.  It is equal to 4 p . 10-7 H/m.
permittivity of free space; electric constant; e0
    The ratio of the electric displacement to the intensity  of  theelectric
field producing it in vacuum.  It is equal to 8.854.10-12 F/m.
Pfund series
    The series which describes the emission  spectrum  of  hydrogen  whenthe
electron is jumping to the fifth  orbital.   All  of  the  linesare  in  the
infrared portion of the spectrum.
Photoelectric effect
    An effect explained by A. Einstein that demonstrate that  lightseems  to
be made up of particles, or  photons.   Light  can  exciteelectrons  (called
photoelectrons) to be ejected from a metal.Light with a  frequency  below  a
certain threshold, at anyintensity, will not cause any photoelectrons to  be
emitted fromthe metal.  Above that  frequency,  photoelectrons  are  emitted
inproportion to the intensity of incident light.    The  reason  is  that  a
photon has energy in  proportion  to  itswavelength,  and  the  constant  of
proportionality is Planck'sconstant.  Below a certain frequency -- and  thus
below a certainenergy -- the incident photons do not have enough  energy  to
knockthe  photoelectrons  out  of   the   metal.    Above   that   threshold
energy,called the workfunction, photons will knock the photoelectrons  outof
the metal, in proportion to the  number  of  photons  (theintensity  of  the
light).  At  higher  frequencies  and  energies,  thephotoelectrons  ejected
obtain a kinetic energy corresponding tothe difference between the  photon's
energy and the workfunction.
Planck constant; h
    The fundamental constant equal to the ratio of the  energy  of  aquantum
of energy to its frequency.  It is the quantum of action.It  has  the  value
6.626196.10-34 J.s.
Planck's radiation law
    A law which more  accurately  described  blackbody  radiation  becauseit
assumed that electromagnetic radiation is quantized.

Poisson spot (S.D. Poisson)
    See Arago spot.  Poisson predicted the  existence  of  such  a  spot,and
actually used it to demonstrate that the wave  theory  of  lightmust  be  in
Principle of causality
    The principle that cause must always preceed effect.   Moreformally,  if
an event A ("the cause") somehow influences an eventB ("the  effect")  which
occurs later in time, then event B cannotin turn have an influence on  event
A.    The principle is best illustrated with an example.   Say  thatevent  A
constitutes a murderer making the  decision  to  kill  hisvictim,  and  that
event B is the  murderer  actually  committing  theact.   The  principle  of
causality puts forth that the act ofmurder cannot have an influence  on  the
murderer's decision tocommit it.   If  the  murderer  were  to  somehow  see
himself committingthe act and change his mind,  then  a  murder  would  have
beencommitted in the future without a  prior  cause  (he  changed  hismind).
This represents a causality violation.   Both  time  traveland  faster-than-
light  travel  both  imply  violations  of  causality,which  is   why   most
physicists think they are impossible, or atleast impossible in  the  general
Principle of determinism
    The principle that if one knows the state to an  infinite  accuracyof  a
system at one point in time, one would be able to predict thestate  of  that
system with infinite  accuracy  at  any  other  time,past  or  future.   For
example, if one were to know all of thepositions and velocities of  all  the
particles in a closed system,then determinism would  imply  that  one  could
then predict thepositions and velocities of those  particles  at  any  other
time.This  principle  has   been   disfavored   due   to   the   advent   of
quantummechanics, where probabilities take an important part  in  theactions
of the subatomic world,  and  the  Heisenberg  uncertaintyprinciple  implies
that one cannot  know  both  the  position  andvelocity  of  a  particle  to
arbitrary precision.
Rayleigh criterion; resolving power
     A  criterion  for  the  how  finely  a  set  of  optics  may  be   able
todistinguish.  It begins with the assumption that central ring ofone  image
should fall on the  first  dark  ring  of  the  other.relativity  principle;
principle of relativity
Rydberg formula
     A   formula   which   describes   all   of   the   characteristics   of
hydrogen'sspectrum,  including  the  Balmer,   Lyman,   Paschen,   Brackett,
andPfund series.
Schroedinger's cat (E. Schroedinger; 1935)
    A thought experiment  designed  to  illustrate  the  counterintuitiveand
strange notions of reality that come along with quantummechanics.
    A cat is sealed inside a closed box; the cat  has  ample  air,food,  and
water to survive an  extended  period.   This  box  isdesigned  so  that  no
information (i.e., sight, sound, etc.) canpass into or out  of  the  box  --
the cat is totally cut off fromyour observations.  Also inside the box  with
the poor kitty(apparently Schroedinger was not too fond  of  felines)  is  a
phialof a gaseous poison, and an automatic hammer to break  it,  floodingthe
box and killing the cat.  The hammer is hooked up to a  Geigercounter;  this
counter is monitoring a radioactive sample and  isdesigned  to  trigger  the
hammer -- killing the cat -- should aradioactive  decay  be  detected.   The
sample is chosen so thatafter, say, one hour,  there  stands  a  fifty-fifty
chance of a decayoccurring.
    The question is, what is the state of the cat  after  that  onehour  has
elapsed?  The intuitive answer is that the cat is eitheralive or  dead,  but
you don't know which until you look.   But  it  is  one  of  them.   Quantum
mechanics, on the other hands, saysthat the wavefunction describing the  cat
is in a superposition ofstates:  the cat is, in fact, fifty per  cent  alive
and fifty percent dead; it is both.  Not  until  one  looks  and  "collapses
thewavefunction" is the Universe forced to choose  either  a  live  cator  a
dead cat and not something in between.
    This indicates that observation also seems to  be  an  importantpart  of
the scientific process -- quite a departure  from  theabsolutely  objective,
deterministic way things used to be withNewton.
Schwarzchild radius
    The radius that  a  spherical  mass  must  be  compressed  to  in  order
totransform it into a black hole; that is, the  radius  of  compressionwhere
the escape velocity at the surface would reach lightspeed.
Snell's law; law of refraction
    A relation which relates the change in  incidence  angle  of  awavefront
due to refraction between two different media.
Speed of light in vacuo
    One of the postulates of A. Einstein's special theory ofrelativity,
which puts forth that the speed of light in vacuum --often written c, and
which has the value 299 792 458 m/s -- ismeasured as the same speed to all
observers, regardless of theirrelative motion.  That is, if I'm travelling
at 0.9 c away fromyou, and fire a beam of light in that direction, both you
and Iwill independently measure the speed of that beam as c.    One of the
results of this postulate (one of the predictionsof special relativity is
that no massive particle can beaccelerated to (or beyond) lightspeed, and
thus the speed of lightalso represents the ultimate cosmic speed limit.
Only masslessparticles (photons, gravitons, and possibly neutrinos, should
theyindeed prove to be massless) travel at lightspeed, and all
otherparticles must travel at slower speeds.
Spin-orbit effect
    An effect that causes atomic energy levels to be split  becauseelectrons
have  intrinsic  angular  momentum  (spin)  in  addition  totheir  extrinsic
orbital angular momentum.
Static limit
    The distance from a rotating black hole where  no  observer  canpossibly
remain at rest (with respect to the distant stars)because of inertial  frame
Stefan-Boltzmann constant; sigma (Stefan, L. Boltzmann)
    The constant of proportionality present in the Stefan-Boltzmannlaw.   It
is equal to

Stefan-Boltzmann law (Stefan, L. Boltzmann)
    The radiated power (rate of emission of electromagnetic energy) ofa  hot
body is proportional to the emissivity, an efficiencyrating,  the  radiating
surface area, and the fourth power  of  thethermodynamic  temperature.   The
constant of proportionality is theStefan-Boltzmann constant.
Stern-Gerlach experiment (O. Stern, W. Gerlach; 1922)
    An experiment that demonstrates the features of  spin  (intrinsicangular
momentum) as a distinct entity apart from orbital angularmomentum.
    The phenomena by which, at  sufficiently  low  temperatures,  aconductor
can conduct charge with zero resistance.
    The phenomena by which, at sufficiently  low  temperatures,  a  fluidcan
flow with zero viscosity.
Superposition principle of forces
    The net force on a body is equal to the sum of the forcesimpressed  upon
Superposition principle of states
     The  resultant  quantum  mechnical   wavefunction   due   to   two   or
moreindividual wavefunctions is the sum of the individualwavefunctions.
Superposition principle of waves
    The resultant wave function due to two or more individual  wavefunctions
is the sum of the individual wave functions.
Thomson experiment; Kelvin effect (Sir W. Thomson [later Lord Kelvin])
     When  an  electric  current  flows  through  a  conductor  whose   ends
aremaintained  at  different   temperatures,   heat   is   released   at   a
rateapproximately  proportional  to  the  product   of   the   current   and
thetemperature gradient.
Twin paradox
     One  of  the  most  famous  "paradoxes"  in   history,   predicted   by
A.Einstein's special theory of relativity.  Take two twins, born onthe  same
date on Earth.  One, Albert, leaves home for a triparound  the  Universe  at
very high speeds (very close to that  oflight),  while  the  other,  Henrik,
stays at  home  at  rests.   Specialrelativity  predicts  that  when  Albert
returns, he will find himselfmuch younger than Henrik.    That  is  actually
not the paradox.  The paradox stems fromattempting to  naively  analyze  the
situation to figure out why.From Henrik's point of view (and  from  everyone
else on Earth),Albert seems to speed off for a  long  time,  linger  around,
and thenreturn.  Thus he should  be  the  younger  one,  which  is  what  we
see.But from Albert's point of view, it's  Henrik  (and  the  whole  of  the
Earth) that are travelling, not  he.   According  to  specialrelativity,  if
Henrik is moving relative to Albert, then Albertshould measure his clock  as
ticking slower -- and thus Henrik isthe one  who  should  be  younger.   But
this is not what happens.
    So what's wrong with our  analysis?   The  key  point  here  is  thatthe
symmetry was broken.  Albert did something  that  Henrik  didnot  --  Albert
accelerated in turning around.  Henrik did noaccelerating,  as  he  and  all
the other people on the Earth canattest to (neglecting gravity).  So  Albert
broke the symmetry, andwhen he returns, he is the younger one.
Ultraviolet catastrophe
    A shortcoming of the Rayleigh-Jeans formula, which attempted  todescribe
the radiancy of a blackbody at  various  frequencies  of  theelectromagnetic
spectrum.  It was clearly  wrong  because  as  thefrequency  increased,  the
radiancy increased without bound;something  quite  not  observed;  this  was
dubbed the "ultravioletcatastrophe."  It was later reconciled and  explained
by theintroduction of Planck's radiation law.
Universal constant of gravitation; G
    The constant of proportionality in Newton's law of  universalgravitation
and which plays an analogous role in A.  Einstein'sgeneral  relativity.   It
is equal to 6.664.10-11 N.m2/kg2.
Van der Waals force (J.D. van der Waals)
    Forces responsible for the  non-ideal  behavior  of  gases,  and  forthe
lattice energy of molecular crystals.  There are three  causes:dipole-dipole
interaction; dipole-induced dipole  moments;  anddispersion  forces  arising
because of small instantaneous dipolesin atoms.
Wave-particle duality
     The  principle  of  quantum  mechanics   which   implies   that   light
(and,indeed, all other subatomic particles) sometimes act  like  a  wave,and
sometime  act  like  a  particle,  depending  on   the   experiment   youare
performing.  For instance, low frequency electromagneticradiation  tends  to
act  more  like  a  wave  than  a  particle;  highfrequency  electromagnetic
radiation tends to act more like aparticle than a wave.
Widenmann-Franz law
     The  ratio  of  the  thermal  conductivity  of  any   pure   metal   to
itselectrical   conductivity   is    approximately    constant    for    any
giventemperature.  This law holds fairly well except at lowtemperatures.
Wien's displacement law
    For a blackbody, the  product  of  the  wavelength  corresponding  tothe
maximum radiancy and the  thermodynamic  temperature  is  aconstant.   As  a
result, as the temperature rises, the maximum ofthe  radiant  energy  shifts
toward the shorter  wavelength  (higherfrequency  and  energy)  end  of  the
Woodward-Hoffmann rules
     Rules  governing  the  formation  of  products  during  certain   types
oforganic reactions.
Young's experiment; double-slit experiment (T. Young; 1801)
    A famous experiment which shows the wave nature of light  (andindeed  of
other particles).  Light is passed from a small sourceonto an opaque  screen
with two  thin  slits.   The  light  is  refractedthrough  these  slits  and
develops an interference pattern on theother side of the screen.
Zeeman effect; Zeeman line splitting (P. Zeeman; 1896)
    The splitting of the lines in a spectrum when the source is  exposed  to
a magnetic field.

Used Literature.

Basic Postulats by Gabrele OHara

Elementary Physic For Students by Bill Strong

Atomic Physic by Steve Grevesone

Optica by Steve Grevesone

Thermodynamics Laws by Kay Fedos
380 622 . 10-23 J

4.10-14 J

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   J   .

5.6697.10-8 W

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