Consider the air / atmosphere – would you say you can ‘see’ air? Consider a blue sky – what are you looking at? You are seeing the atmosphere (combination of gases), and it looks blue because that parts of the spectrum is scattered by air molecules more tha the other visible wavelengths of the visible spectrum. Welcome to the world of identifying a gas (or gases) from its interaction with light.
Comments
Andrew commented on :
Many gasses are coloured so they can be seen. E.g. bromine gas is a brown colour.
Steve P commented on :
Consider the air / atmosphere – would you say you can ‘see’ air? Consider a blue sky – what are you looking at? You are seeing the atmosphere (combination of gases), and it looks blue because that parts of the spectrum is scattered by air molecules more tha the other visible wavelengths of the visible spectrum. Welcome to the world of identifying a gas (or gases) from its interaction with light.