The tungsten filament lamp is heated up to 2900 º C to emit light.At such high temperature the tungsten oxidized and bulb gets damaged. So, to prevent oxidation of tungsten filament, electric bulbs are filled with nitrogen or inert gases like helium, neon or argon.
Bulbs are filled with chemically inactive Nitrogen or Argon gas to prevent the oxidation of tungsten filament used in the bulb.
A bulb is filled with an inert gas such as argon or nitrogen slows down the evaporation of the tungsten filament compared to operating it in a vacuum. This allows for greater temperature and therefore results in greater efficiency of filament life.
In a bulb , nitrogen gas ( inert gas ) . is filled because in the bulb filament tungsten is there the melting point of tungsten in 3422°C and when electric city is passed it emits the light but doesn't melt . and the nitrogen gas is filled in the bulb so the bulb should not get burnt .
The filament in an electric bulb is made using tungsten which would burn quickly when it comes in contact with the oxygen in the air. This is the reason why gases that are not reactive such as argon and nitrogen are used for filling an electric bulb.
Argon is a commonly used gas used to fill incandescent light bulbs. It increases bulb life by preventing the tungsten filaments from deteriorating too quickly. Other gases such as helium, neon, nitrogen and krypton are also used in lighting.