The laws list
L


L to Lyman series.


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L.

 L

See Avogadro constant.
 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 proportional to the cosine of the
angle with the normal.
 Lambert's third law

The luminous intensity of light decreases exponentially
with distance as it travels through an absorbing medium.
 Lagrange points

Points in the vicinity of two massive bodies (such as the Earth
and the Moon) where each others' respective gravities balance.
There are five, labelled L1 through L5. L1, L2, and L3 lie
along the centerline between the centers of mass between the
two masses; L1 is on the inward side of the secondary, L2 is
on the outward side of the secondary; and L3 is on the
outward side of the primary. L4 and L5, the socalled Trojan
points, lie along the orbit of the secondary around the
primary, sixty degrees ahead and behind of the secondary.
L1 through L3 are points of unstable equilibrium; any
disturbance will move a test particle there out of the
Lagrange point. L4 and L5 are points of stable equilibrium,
provided that the mass of the secondary is less than about 1/24.96 the
mass of the primary. These points are stable because
centrifugal pseudoforces work
against gravity to
cancel it out.
 Landauer's principle

A principle which states that it doesn't explicitly take energy to
compute data, but rather it takes energy to erase any data,
since erasure is an important step in computation.
 Laplace equation (P. Laplace)

For steadystate heat conduction in one dimension, the temperature
distribution is the solution to Laplace's equation, which states
that the second derivative of temperature with respect to
displacement is zero; mathematically,
d^{2} T/dr^{2} = 0.
 Laue pattern (M. von Laue)

The pattern produced on a photographic film when highfrequency
electromagnetic waves (such as xrays) are fired at a crystalline
solid.
 laws of blackhole dynamics

See blackhole dynamic laws.
 law of parismony

See Occam's razor.
 laws of thermodynamics

See thermodynamic laws.
 Lawson criterion (J.D. Lawson)

A condition for the release of energy from a thermonuclear
reactor. It is usually stated as the minimum value for the
product of the density of the fuel particles and the energy
confinement time for energy breakeven. For a halfandhalf
mixture of deuterium and tritium at ignition temperature, n_{G} tau
is between 10^{14} and 10^{15} s/cm^{3}.
 Le Chatelier's principle (H. Le Chatelier; 1888)

If a system is in equilibrium, then any change imposed on the
system tends to shift the equilibrium to reduce the effect of that
applied change.
 lefthand rule

The oppositechirality version of the righthand rule.
 Lenz's law (H.F. Lenz; 1835)

An induced electric current always flows in such a direction that
it opposes the change producing it.
 Loschmidt constant; Loschmidt number; N_{L}

The number of particles per unit volume of an ideal gas at
standard temperature and pressure. It has the value 2.687 19 x
10^{25} m^{3}.
 lumen; lm

The derived SI unit of luminous flux, defined as the luminous flux
emitted by a uniform point source of 1 cd emitting its luminous
energy over a solid angle of 1 sr; it thus has units of cd sr.
 lumeniferous aether

A substance, which filled all the empty spaces between matter,
which was used to explain what medium light was "waving" in. Now
it has been discredited, as Maxwell's equations imply that
electromagnetic radiation can propagate in a vacuum, since they
are disturbances in the electromagnetic field rather than
traditional waves in some substance, such as water waves.
 lux; lx

The derived SI unit of illuminance equal to the illuminance
produced by a luminous flux of 1 lm distributed uniformly over an
area of 1 m^{2}; it thus has units of lm/m^{2}.
 luxon

A particle which travels solely at c (the speed of light in
vacuum). All luxons have a rest mass of exactly zero. Though
they are massless, luxons do carry momentum. Photons are the
prime example of luxons (the name itself is derived from the Latin
word for light).
Compare tardon, tachyon.
 Lyman series

The series which describes the emission spectrum of hydrogen when
electrons are jumping to the ground state. All of the lines are
in the ultraviolet.

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