| The laws list: L |
The laws list L
L to Lyman series.
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L.
- 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.
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- 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
so-called 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 steady-state 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,
d2 T/dr2
= 0.
- Laue pattern (M. von Laue)
-
- The pattern produced on a photographic film when
high-frequency electromagnetic waves (such as x-rays) are fired at a
crystalline solid.
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 half-and-half mixture of deuterium and tritium
at ignition temperature, nG tau is between 1014
and 1015
s/cm3.
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.
left-hand rule
The opposite-chirality version of the
right-hand 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;
NL
The number of particles per unit volume of an
ideal gas at standard temperature and pressure. It has the value 2.687 19 x
1025
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
m2;
it thus has units of
lm/m2.
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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