An LED light bulb is a solid-state lighting (SSL) device that fits in standard screw-in connections but uses LEDs (light-emitting diodes) to produce light. LED light bulbs are a more environmentally-friendly alternative to incandescent bulbs. LED bulbs use a semiconductor device that emits visible light when an electric current passes through it. That property is known as elecroluminescence. Compact fluorescents, the most common alternative to incandescent bulbs, use electricity to excite mercury gas until it emits ultraviolet (UV) light. That light is then passed through a phosphor, which causes it to emit more visible light. LEDs themselves have been around for some time, but only recently have improvements in efficiency, cost and output made them viable for the larger-scale lighting used in households, businesses and other environments. Due to the rapid progress in LED technologies, products exist with wide ranges of efficiencies and life spans. The bulbs can work for 50000 hours, if not run outside of the specified temperature range. They use about 8-11 watts of power to replace a 60-watt incandescent with at least 806lumen and 9.5 watts for a 75-watt equivalent. This capacity provides an efficiency gain of up to 80% over incandescent bulbs. Other benefits of LED light bulbs: (1) Cooler than incandescent bulbs in operation. (2) Instant on, unlike compact fluorescent bulbs. (3) Broad range of color possibilities. (4) Customizable lights can be controlled through a Bluetooth connection. (5) Lowest cost over ownership of all lights. (6) No mercury and minimal toxic materials required. (7) A single lamp represents a reduction of hundreds of pounds of CO2, compared to use of incandescents. (8) Possible simultaneous use in data transfer with LiFi. However there also some caveats. Research indicates that some wavelengths may be damaging to eyes over time. Furthermore, toxic metals are used to produce some wavelengths of lights, which would increase the environmental impact of those particular bulbs