Electric Bulb has NO Vacuum inside, instead the bulb is filled with Argon Gas or argon mixed Nitrogen gas inside, which is one of the Latest Electronic Technology in recent times.
In early days, Vacuum is left inside electric bulbs, to prevent the burning of Tungsten filament at high temperatures of about 2000 degree Celsius.
Creating Vacuum inside bulb results lack of air pressure, which substantially leads to evaporation.
However, this Tungsten filament is sealed in oxygen free chamber to prevent from catching fire.
But, Tungsten filament loses its atoms at this high temperature and started evaporating carbon gases accumulating in walls of bulb, thus reduces the lifetime of bulb.
Though the bulb has no vacuum, it also has no oxygen, which prevents oxidation or combustion.
Studies were carried out to enhance the lifetime of bulb and minimize the expenditure of energy from tungsten.
Hence, i)Tungsten filament has twisted into strands in the form of spring like coils between electrodes for better durability.
ii)Filling Argon (inert gas prevents combustion) or argon mixed gas has no chemical reaction, thus it doesn’t affect the working of Tungsten filament and also the gas prevents evaporation of the filament, increasing the lifetime of the bulb.