| The laws list: B |
The laws list B
Balmer series to Brownian motion.
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B.
- Balmer series (J. Balmer; 1885)
-
- An equation which describes the emission
spectrum of hydrogen when an electron is jumping to the second orbital; four
of the lines are in the visible spectrum, and the remainder are in the
ultraviolet.
-
- baryon decay
-
- The idea, predicted by several grand-unified theories, that a class of
subatomic particles called baryons (of which the nucleons -- protons and
neutrons -- are members) are not ultimately stable but indeed decay. Present
theory and experimentation demonstrate that if protons are in fact unstable,
they decay with a halflife of at least ~1034 y.
-
- beauty criterion (Dirac)
-
- The idea that the more aesthetically pleasing
a theory is, the better it is. Naturally this criterion does not stand up to
the real test -- whether or not predictions of a given theory agree with
observational tests -- but considering that it is a purely aesthetic quality
that is being tested, many of the most successful theories (special
relativity, general relativity, quantum electrodynamics, etc.) match the
criterion particularly well.
-
- becquerel; Bq (after A.H. Becquerel,
1852-1908)
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- The derived
SI unit of
activity, defined as the activity of a radionuclide decaying at a rate, on
the average, of one nuclear transition every 1
s; it
thus has units of
s-1.
-
- Bernoulli's equation
-
- In an irrotational fluid, the sum of the
static pressure, the weight of the fluid per unit mass times the height, and
half the density times the velocity squared is constant throughout the
fluid.
-
- Bell's inequality (J.S. Bell; 1964)
-
- A quantum mechanical theorem which
demonstrates that if quantum mechanics were to rely on hidden variables, it
must have nonlocal properties.
-
- BCS theory (J. Bardeen, L.N. Cooper, J.R.
Schrieffer; 1957)
-
- A theory put forth to explain both
superconductivity and
superfluidity. It suggests that in the superconducting (or superfluid)
state electrons form Cooper pairs, where two electrons act as a single unit.
It takes a nonzero amount of energy to break such pairs, and the
imperfections in the superconducting solid (which would normally lead to
resistance) are incapable of breaking the pairs, so no dissipation occurs
and there is no resistance.
-
- Biot-Savart law (J.B. Biot, F. Savart)
-
- A law which describes the contributions to a
magnetic field by an electric current. It is analogous to
Coulomb's law. Mathematically, it is
dB = (mu0
I)/(4 pi r2) dl cross e
where dl is the infinitesimal directed length of the electric
current causing the magnetic field, I is the current running through
that directed length, r is the distance from that directed length,
and e is the unit vector directed from the test point to
current-producing length. -
- blackbody radiation
-
- The radiation -- the radiance at
particular frequencies all across the spectrum -- produced by a blackbody --
that is, a perfect radiator (and absorber) of heat. Physicists had
difficulty explaining it until Planck introduced his
quantum of action.
-
- black-hole dynamic laws; laws
of black-hole dynamics
-
-
- first law
of black hole dynamics
-
- For interactions between black holes and normal matter, the
conservation laws of
mass-energy,
electric charge,
linear momentum, and
angular momentum, hold. This is analogous to the
first law of thermodynamics.
- 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. This is analogous to the
second law of thermodynamics, with the surface areas of the black
holes being a measure of the entropy of the system.
-
- Bode's law, Titius-Bode law
-
- A mathematical formula which generates, with a
fair amount of accuracy, the semimajor axes of the planets in order out from
the Sun. Write down the sequence
0, 3, 6, 12, 24, ...
and add 4 to each term:
4, 7, 10, 16, 28, ...
Then divide each term by 10. This leaves you with
the series
0.4, 0.7, 1.0, 1.6, 2.8, ...
which is intended to give you the semimajor axes
of the planets measured in astronomical units.
Bode's law had no theoretical justification
when it was first introduced; it did, however, agree with the
soon-to-be-discovered planet Uranus' orbit (19.2 au actual; 19.7 au
predicted). Similarly, it predicted a missing planet between Mars and
Jupiter, and shortly thereafter the asteroids were found in very similar
orbits (2.77 au actual for Ceres; 2.8 au predicted). The series, however,
seems to skip over Neptune's orbit. The form of Bode's law (that is, a
roughly geometric series) is not surprising, considering our theories on the
formation of solar systems, but its particular formulation is thought of as
coincidental. -
- Bohr magneton (N. Bohr)
-
- The quantum of magnetic moment.
-
- Bohr radius (N. Bohr)
-
- The distance corresponding the mean distance of an
electron from the nucleus in the ground state of the hydrogen atom.
-
- Boltzmann constant; k (L.
Boltzmann)
-
- A constant which describes the relationship
between temperature and kinetic energy for molecules in an ideal gas. It is
equal to 1.380 622 x 10-23
J/K.
-
- Boyle's law (R. Boyle; 1662);
Mariotte's law (E. Mariotte; 1676)
-
- The product of the pressure and the volume of
an ideal gas at constant temperature is a constant.
- Brackett series (Brackett)
-
- The series which describes the emission
spectrum of hydrogen when the electron is jumping to the fourth orbital. All
of the lines are 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 the layers of atoms or ions are regularly separated, the
maximum intensity of the reflected ray occurs when the complement of the
angle of incidence, theta, the wavelength of the x-rays,
lambda, and the distance betwen layers of atoms or ions, d, are
related by the equation
2 d sin theta = n lambda,
where n is an integer. -
- Brewster's law (D. Brewster)
-
- The extent of the polarization of light
reflected from a transparent surface is a maximum when the reflected ray is
at right angles to the refracted ray.
-
- Brownian motion (R. Brown; 1827)
-
- The continuous random motion of solid
microscopic particles when suspended in a fluid medium due to the
consequence of ongoing bombardment by atoms and molecules.
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