Физические законы, переменные, принципы
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
sametemperature.
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
normal.
Lambert's third law. The luminous intensity of light decreases
exponentially with the distance that it travels through an absorbing
medium.
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
crystallinesolid.
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
destroyed.
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
zero.
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
ultraviolet.
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
polarizer.
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
flow.
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
surface.
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
electron.
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
junction.
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
error.
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
sense.
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
dragging.
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.
Superconductivity
The phenomena by which, at sufficiently low temperatures, aconductor
can conduct charge with zero resistance.
Superfluidity
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
it.
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
spectrum.
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 O’Hara
«Elementary Physic For Students» by Bill Strong
«Atomic Physic» by Steve Grevesone
«Optica» by Steve Grevesone
«Thermodynamic’s Laws» by Kay Fedos
-----------------------
380 622 . 10-23 J
K.
4.10-14 J
m3.
Km .
s.Mpc
J .
K.mol
5.6697.10-8 W
m2.K4.
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