Most of the incandescent light bulbs are filled with the combination of two gases i.e. 93% of argon and 7% of nitrogen. Higher vapor pressure of argon gas reduces evaporation process of the tungsten filament in the Light bulb and its low thermal conductivity reduces conductive cooling of the filament. Since, argon has comparative low breakdown voltage, small amount of nitrogen gas approximately 7% is added for the prevention of arcing between filament supports of light bulb.
Some high-brightness halogen light bulbs are filled with the combination of argon and small amount of halogen gas mostly bromine or iodine. The halogen gas combines with evaporated tungsten from the filament then, the resulting tungsten-halogen compound breaks down when it gets in contact with the hot tungsten filament and re-deposit the evaporated tungsten back onto the filament. This process allows the filament to run more reliably at a higher temperature than a normal incandescent lamp and called the halogen cycle.
Hence, we can say that argon, nitrogen and halogens (like bromine or iodine) are the gases present inside the light bulbs. The main purpose of gases are to highly reduce the rate of evaporation of tungsten from the filament of the light bulbs. They highly increases the lifespan of the light bulbs and make it stay glowing for lighting purpose i.e prevents the tungsten filament from burning out too quickly.
Conclusion
Hope, you have clearly understand about the gas present inside light bulb and the reason why is gas present in light bulbs. Make sure to leave your opinion and suggestion about this post in the Comment section Below.