Popular in offices, schools, warehouses, and other industrial settings, fluorescents are efficient and reliable light sources. Because they run cooler and have an operating life ten to twenty times longer than standard incandescents, fluorescent lights are also increasingly found in residences—especially in heavy-use areas such as kitchens, garages, and basements.
Parts Overview
Fluorescent lights feature a glass tube sealed at low pressure. Inside is a small amount of mercury, along with an inert or inactive gas, which is typically argon. Inside the tube is also a coating of phosphor powder (a chemical compound that emits light when exposed to light of a different wavelength), as well as two electrodes—one at each end of the tube. (See diagram.) These electrodes are wired to an electrical circuit, which is powered by connecting it to an alternating current, or AC, supply.
The Science: How They Work
- When you turn on a fluorescent light, voltage is induced and a current flows through the circuit to the electrodes.
- This voltage causes electrons to flow down the length of the tube.
- The energy created causes some of the mercury to transform from a liquid into a gas state.
- As some of the electrons collide with the gaseous mercury atoms, the atoms are excited into a higher energy state.
- When the electrons return to their original energy level, they release light photons.
- These ultraviolet (UV) wavelength photons can’t be seen by the human eye. However, when they collide with the phosphor powder coating inside a bulb or tube, it produces visible white light.
- One of the main reasons fluorescents are more efficient than incandescents is because energy is mostly converted into light. With incandescents, the energy is turned into heat.
Types of Fluorescents
Fluorescent lights come in various types and shapes, including compact fluorescent lamps (CFLs) and also in long tubes that frequently hang from ceiling fixtures. Many other common forms of lighting are also made from fluorescents.
- Tanning lamps feature a different phosphor powder blend than standard fluorescent lights, which can trigger a tanning effect on human skin.
- In Black lights, the glass tube is coated with a phosphor that changes the short-wave UV light to a long-wave UV instead of visible “white” light.
- With Grow lamps, the phosphor blends used inside the tube emit light in the red and blue color range to spur photosynthesis in plants.
Fluorescents vs. Incandescents
Despite the inefficiencies of incandescents, many people still prefer them for home use because they emit what’s considered a “warmer” light, meaning it provides more reds from the color spectrum and less “cooler” blues. Some of the other often-referenced disadvantages of fluorescents include:
- Shortened life-span when switched on and off frequently. This is commonly due to the erosion of the electron-emitting surface of the cathodes—the metallic electrode through which current flows—every time the light goes on and off and begins a new start cycle.
- Lamp shape. While compact fluorescent lamps (CFLs) can replace incandescents in most fixtures, there are situations where the space will not accommodate CFLs.
- Dimmer compatibility. Fluorescent light fixtures cannot be connected to dimmer switches made specifically for incandescent lamps.
- Noise and flickering from ballasts. Fluorescent lamps need a ballast, a magnetic device that controls the current load that runs through the lamp. This current can produce a noticeable hum or buzz sound, as well as create a flicker that can cause issues for those with a sensitivity to light.
- Ultraviolet (UV) light exposure. The small amount of ultraviolet (UV) light emitted from fluorescents can mimic the light from sun exposure, which can be potentially dangerous over large amounts of time. This UV light also could require some protection for items such as valuable or historical artifacts that sit in museums, as it could degrade surface materials and cause permanent damage.
- Potentially harmful mercury content. Perhaps the biggest downside to fluorescent lights is the small amount of mercury found inside, as well as in the phosphor coating. This mercury is considered hazardous material, which means broken lights that are not properly cleaned may release dangerous chemicals into the soil or water supply. Broken or used fluorescents should always be taken to dedicated facilities for proper recycling.
To encourage energy savings, many local municipalities in the United States—and several countries including many in East and Southeast Asia—have phased out the use of incandescent lights in favor of fluorescents. Now that you’re more knowledgeable about how they work, as well as their pros and cons, you can choose the lighting that works best for your home, office, or work environment.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.