Fluorescence and efficiency, by Tomás Unger

In last week’s column We explain the discovery and development of the incandescent light bulb. Invented in the 19th century and perfected over more than 100 years. However, the energy inefficiency of the incandescent bulb, which converts only 5% of electricity into light, prompted the search for other sources of light. illumination.

A series of discoveries, beginning with that of Francis Hauksbee, who generated bluish illumination by electrifying mercury vapor (1707), combined to produce a commercial fluorescent light in the late 19th century.

—Gasses and colors—

The term ‘fluorescent’ describes the quality of certain materials that emit light by being irradiated with another type of energy. , a small lightning bolt or arc that jumps from one electrode to another through gas inside a glass capsule.

The invention was unsuccessful as it required a lot of energy to produce a amount of light very limited. But eventually, the idea of ​​an electric arc was combined with the discovery of the fluorescence of various gases and minerals. Inside a capsule, an electric arc could ignite the fluorescence of some gases, such as mercury vapor.

“LED bulbs emit light by jumping electrons between bands of atoms in the semiconductor.”

The color of the light that gases emit – the visible light spectrum of their fluorescence – varies from gas to gas. At first, fluorescent lights were used for decoration and advertising, since their coloration did not make them very useful as a light source. However, a new material finally brought them useful: This light, in turn, can activate the fluorescence of solid materials that give other ranges of visible light, crucially white light.

Thus, by coating the interior of a glass bulb or tube with material whose fluorescence gives off white light, and filling the interior with a fluorescent gas that produces ultraviolet light, electrodes can be placed at the base to create an electric arc inside. The electric arc does not produce much light, but it activates the fluorescence of the gas, and its ultraviolet radiation activates the fluorescence of the material that lines the interior of the glass.

—Tubes and bulbs –

The neon tube, with an electrical contact and a white or colored glass tube and gas inside, was massively marketed in the 1930s, when General Electric acquired the patent. Their consistency of light, lower electricity consumption and durability, gave fluorescent lamps a greater advantage over incandescent bulbs, especially in commercial or industrial environments, which required abundant continuous light.

These are shaped like a traditional light bulb, but contain small tubes whose combined surface area is comparable to that of a large tube.

—Advantages and dangers—

CFLs are more efficient than incandescent bulbs, using 20% electricity to produce luminosity. They also have a lifespan between four and eight times longer, although their durability is shortened if they are switched on and off frequently. They also cannot be used in closed lamps, as overheating shortens their life and can cause them to burst.

If they do not have an encapsulation to filter it, skin exposed to a nearby CFL can receive radiation similar, although less, to that of the sun without sunscreen. However, the main disadvantage of CFLs is their mercury content, a toxic material that, when the bulb breaks, can escape and be inhaled or absorbed through the skin.

—Another brilliant idea—

The electroluminescence of some materials, the brightness resulting from the passage of a electric current, was discovered in 1907 by the Englishman Joseph Round. The Russian Oleg Losev created in 1927 the first light-emitting diode (LED), a semiconductor material that, in turn, conducts electricity and opposes resistance.

Today’s variety of applications and the physics behind LED technology warrant a separate page. For the purposes of the evolution of lighting, suffice it to say that, unlike incandescent bulbs, which produce light when heated,

Driven by the electric power, jumps release photons or light particles: electroluminescence. The color of the resulting light depends on the mixture of semiconductor materials, many of which are gallium compounds. The first commercial applications occurred in the 1960s, first with small infrared light emitting bulbs, and then with red light, useful for dashboards and instruments.

The white or yellowish light of today’s spotlights is the result of a sustained development of decades and was achieved by combining materials. Its energy efficiency and absence of toxic materials make the LED bulb, despite its higher initial cost,

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