I'm going through some notes and came upon a question... So, the absorption sepctrum can be seen when a gas sample is placed in the path of white incandescent light where the light absorbes descrete wavelengths. I read that only some of these absorption lines appear if the gas is cool, but if the gas is hot, additional lines will appear. My question is how to explain why the quantity of absorption lines visible is dependent upon the initial temperature of the gas sample? I would say this has something to do with the energy of the atoms at high and low temps. but this would indicate the length of the wavelengths present, not the amount. Correct? Any advice is appreciated.