The common light bulb has seen some significant improvements since its invention in the 19th century. The most noteworthy advances have been made in energy-efficiency and environmental friendliness.
This article explains the working principle of four different household light sources, as well as some of their positive and negative aspects.
The breakthrough in household lighting came about in 1879, when Thomas Edison invented the first commercially practical incandescent light. Incandescent light bulbs are still commonly used around the world, but moves have been made by different governments to gradually phase out these types of bulbs.
Incandescent light bulbs produce light when a filament wire inside the bulb is heated to a high temperature by an electrical current passing through the wire. This makes the wire glow.
Incandescent globes are often an attractive choice in shops because their initial purchase price is less per bulb than other types of light bulbs.
However, most of the energy generated by these bulbs is lost through heat and a mere 10% of the energy used produces light. The lifespan the bulb is comparatively short as well, and in the long run they often tend to be more expensive than their more modern counterparts.
An exception to the above is the Centennial light, also known as the world's longest-reflecting light bulb, having burned for at least 110 years. The extraordinary bulb is located in Livermore, California and even has its own webcam.
To produce light, fluorescent globes use electricity to excite mercury vapor, which in turn produces short-wave ultraviolet light. The ultraviolet light in turn causes a phosphor to fluoresce, which produces visible light.
Compared to the incandescent light bulbs, fluorescent lighting uses less power for a given amount of light output and is there before more effective at turning energy into visible light.
The downside of fluorescent globes is their environmental impact. As the lamps contain mercury, they are classified as hazardous waste and are there harder to dispose of.
Their purchase price is higher than incandescent light bulbs but they last longer, which makes them more affordable in the long run.
Halogen globes are essentially an advanced form of incandescent globes. Just like in incandescent light globes, the filament in halogen globes consist of ductile tungsten and is located in a gas-filled globe. What makes them different from incandescent globes, however, is that the gas in halogen globes is at a higher pressure and the globe is stronger to contain the higher pressure.
Halogen globes are typically considered as being more energy-efficient than incandescent globes, and they produce light that is stronger and whiter than produced by incandescent lighting. They do not contain any mercury either, and are there easier to dispose of than fluorescent lamps.
The downside of halogen lighting is that the globes can heat up quickly and cause burns if touched. They are also more expensive than incandescent globes. However, similar to the fluorescent lamps, they tend to last longer, since ending up costing as much as incandescent globes in the long run.
Light-Emitting Diodes, or LEDs for short, produce light by a phenomenon called electroluminescence in a semiconductor material. Electroluminescence is the phenomenon of a material emitting light when electric current is passed through it.
LED lighting is generally the most energy-efficient lighting available for households at the moment, as well as being the lighting option with the longest lifespan. LED lights are also very energy-efficient and they are not as fragile as other globes made of glass, making them safer for everyday use.
They can be somewhat expensive although compared to the other alternatives, and tend to dim over time as the globe ages. Also, they do not perform that well in conditions where the variations between summer and winter temperatures are high.