Laser

(n.m.) Primary source of very powerful monochromatic light (a single colored light). Lasers are found in CD and DVD players, on construction sites, in surgery (for operations), in astronomy (to measure the Earth-Moon distance to within 20 cm), and on roads for speed control.

Law of Uniqueness

(n.f.) The concerned quantity (intensity, voltage) retains the same value.

LED (Light Emitting Diode)

(n.) A diode that allows electrical current to pass in only one direction and emits light.

Lens

(n.f.) Transparent block possessing an axis of symmetry called the optical axis. There are divergent lenses and convergent lenses.

Light Diffusion

(n.) The process of scattering light in all directions. In foggy conditions, the light beam from a car's headlights is diffused by water droplets suspended in the atmosphere. The light is diffused, and the headlights, instead of illuminating the asphalt, light up the surrounding fog. Therefore, the brighter the headlights, the less visible the road becomes, and the more the fog is illuminated. Fog lights are directed towards the lower part of the road. Their beam passes under the fog, which floats about twenty centimeters above the road. This illuminates the asphalt and very little of the fog.

Light Filter

(n.) A pane of glass or plastic that absorbs certain colored lights and allows others to pass through.

Light Year

(n.) Distance traveled by light in a vacuum in one year (Symbol ly). One light year is equal to 946 billion kilometers (9.46 x 10¹⁵ m). The closest star to our Sun is Proxima Centauri, located 4.3 light years from our star. The average size of a spiral galaxy like our Milky Way is about 100,000 light years. The galaxy closest to ours is the Andromeda galaxy, which is 2.2 million light years away. The size of the universe is estimated to be 15 billion light years.

Limewater

(n.) A colorless liquid used to identify the presence of carbon dioxide. Limewater becomes cloudy in the presence of carbon dioxide.

Liquefaction

(n.f.) Transition from the gaseous state to the liquid state.

Liquid

(n.m.) One of the three states of matter. A liquid has no shape of its own. It takes the shape of the container that holds it. Its free surface at rest in wide containers is flat and horizontal. It is a compact and disordered state of matter.

Liter

(n.m.) Unit of capacity (volume). Symbol L. 1000 L = 1 m³.

Loop (electrical)

(n.f.) An electrical path that goes from the + terminal to the - terminal of the generator.

Luminous Ray

(n.) A line along which light propagates. A luminous ray is represented by a straight line oriented by an arrow going from the light source to the illuminated object.

Lunation

(n.f.) Duration between two consecutive new moons.