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Index (L)

LA - LC

LD - LF

LG - LJ

LK - LN

LO - LR

LS - LV

LW - LZ

Moment of truth
The fastest man-made object that ever leave the Earth is the Pinoeer 10 spacecraft, launched in 1972, and attained a speed of more than 32000 mph.


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lumen Metro.
A latin word for light, lumen is the SI unit (abbreviation: lm) for measuring the luminous flux produced by a light source equal to the intensity of 1 candela (Cd) in a solid angle of 1 steradian. In other words, it is the amount of light which falls on unit area of surface at a unit distance from a source of 1 Cd.

luminosity Phys.
The visual perception of the brightness of an object, or the density of luminous intensity in a particular direction.

luminosity class Astron.
The total energy (including light) radiated by a star at all wavelengths, in a second. It is one of the basic properties for star characterization. A luminosity classification scheme is used to compare the brightness of stars with the same temperature or spectral class.

Luminosity class

Star type

Ia

largest supergiants

Ib

supergiants

II

bright giants

III

giants

IV

subgiants

V

dwarfs

VI

subdwarfs

wd

white dwarfs

Luminosity class V stars are also known as main-sequence stars because most of the stars fall on this category. A star's luminosity is roughly equal to the cube of a star's mass.

lux Metro.
The SI unit, symbol lx, of measuring illuminance which is equal to the illumination produced by a luminous flux of 1 lumen distributed uniformly over an area of 1 square meter (1 lx = 1 lm/m2).

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