Incandescent light bulb Small variations in resistivity along the filament cause "hot spots" to form at points of higher resistivity; a variation of diameter of only 1% will cause a 25% reduction in service life. These hot spots evaporate faster than the rest of the filament, which increases the resistance at that point—this creates a positive feedback that ends in the familiar tiny gap in an otherwise healthy-looking filament. Irving Langmuir found that an inert gas, instead of vacuum, would retard evaporation. General service incandescent light bulbs over about 25 watts in rating are now filled with a mixture of mostly argon and
Phase-out of incandescent light bulbs been initiated by the Ministry of Energy where three CFLs will be sold at a subsidized price to the public. Qatar has banned incandescent light bulbs. South Korea has phased out incandescent light bulbs under 150 watts since 2014. The government has prohibited manufacture and import of all incandescent lights. All incandescent bulbs are going to be replaced by LED and CFL light bulbs. Taiwan banned incandescent bulbs in 2012. Tajikistan reportedly banned incandescent light bulbs in 2009 to save energy, though this was criticised as alternatives were expensive at the time. The UAE has banned incandescent light bulbs. Uzbekistan