Let there be fluorescent light! Fluorescent lights are found everywhere, but do you know how they work? Those white tubes are more efficient than incandescent bulbs and don't get as hot. Take our quiz to see how much you know about the science inside these fluorescent lamps.
Light is a form of energy that is released by an atom. It consists of many small particlelike packets that have energy and momentum but no mass.
The most basic units of light are photons, which are released from atoms when their electrons become excited.
An excited electron holds its position for just a fraction of a second, then is drawn back toward the nucleus to its original orbit. As it returns to its original orbit, the electron releases extra energy in the form of a photon.
In an ordinary incandescent light bulb, atoms are excited by heat. In a light stick, atoms are excited by a chemical reaction. Fluorescent lights have a much more complex system for exciting atoms.
The sealed tube contains a tiny bit of mercury and an inert gas, commonly argon.
When you turn on a fluorescent lamp, the current flows through the electrodes, which starts the movement of electrons from one end of the tube to the other.
The electrons in mercury atoms mostly release photons in the ultraviolet wavelength range. Human eyes cannot see ultraviolet photons, so they must be converted to visible light.
The inner part of the sealed tube contains a phosphor powder coating. Phosphors emit light in the visible spectrum when they are exposed to ultraviolet light energy.
Incandescent light bulbs emit quite a bit of ultraviolet light, which is not converted to visible light, and they also emit more heat than fluorescent lamps, losing more energy in the process.
Although a typical fluorescent lamp is four to six times more efficient than an incandescent lamp, most people still use incandescent lights because they emit a "warmer" light.
Ions are atoms that have lost or gained an electron. These charged atoms are drawn to oppositely charged areas, just like electrons.
In a gas, an electrical charge is carried by free electrons or ions when there is a difference in charge between the two ends of the tube, i.e. voltage.
Neon lights are gas discharge lamps that release colored visible light. Many street lights use a similar system with different gases.
There are few ions and free electrons in a gas, so the first thing a fluorescent lamp needs to do is release many new free electrons from both electrodes.
The conventional starter switch has a small gas discharge bulb, which boils off electrons from a metal surface and sends them into the main tube and ionizes the gas inside.
Older fluorescent lamps take a few seconds to light up because the conventional starter switches take a few seconds to create enough ionizing gas for the main tube to start glowing.
A high initial voltage across the electrodes causes an excess of electrons on the electrode, with some electrons moving into the gas of the tube. This process, known as a corona discharge, ionizes the gas and sets off the electrical arc that lights the tube.
In a gas discharge circuit, such as a fluorescent lamp, electric current causes resistance to decrease. This is because as more electrons and ions flow through a particular area, they bump into more atoms, which frees up electrons and creates more charged particles.
The simplest sort of ballast, a magnetic ballast, works like an inductor. It consists of a wire coil in a circuit, wound around a piece of metal, that works by opposing a change in the current flowing through it.
Magnetic ballasts limit the electrical current at a low cycle rate, which can cause the light to flicker and also results in the humming sound that you might associate with older fluorescent lamps.