Modern light bulbs

In flasks of modern lights light bulbs tungsten spiral. Electric current, pronyma spiral, heats it almost to 2700°C, causing radiation dazzling white light.
The light that emits the lamp, measured in lumens. The ratio between the amount of light and power by electricity is called luminous efficiency. Light efficiency of a lamp that has a tungsten spiral, equal to about 12 lumens/watt. In other words, we are talking about the low efficient light source. The overwhelming proportion of the radiation of a spiral is in the invisible infrared, or heat spectrum. Another problem is that the atoms of tungsten evaporate from the surface of a spiral deposited on the inner surface of the flask. Gradually blackens the bulb. In the end, the tungsten evaporates so that the coil burns out and the lamp goes out.
To slow the evaporation of a spiral, bulb lamps filled with argon and nitrogen, but to get rid of it forever impossible. The higher the temperature of the spiral, the faster the evaporation, while the light becomes brighter and prirodnie. Producers managed to achieve some compromise, and the modern bulbs available resource approximately 1000 hours, but in their emitted spectrum is more yellow than the sun. Energy saving light bulbs consume less electricity and last ten times longer, but cost more.