Line emission and absorption spectra
Studying the line spectra produced by hot gases and absorbed by cooler gases allows us to identify the elements in stars.
When matter is very hot it emits light. This light, when seen through a prism or A piece of material with lines on it that produce a spectrum which diffuses light., shows all wavelengths of visible light. This is called a A complete spectrum of colours showing all wavelengths of light.. A light source, such as a star or a filament bulb, gives a continuous emission spectrum.
When a gas is very hot, it doesn’t emit all wavelengths of light. Hot gases don’t produce a continuous emission spectrum.
A hot gas only emits certain wavelengths of light to produce bright lines on a dark background. This is called a A series of bright lines on a dark background. Produced by hot gases.. A gas cloud on its own, without a light source behind it, produces a line emission spectrum.
When a gas is cool, it absorbs the same wavelengths of light as it would emit when it is hot. So if a continuous spectrum travels through a cooler gas, it will ‘pull out’ or absorb certain wavelengths of light to produce a series of dark lines on a continuous spectrum of light. This is called a A series of dark lines on a continuous emission spectrum. Produced by a cool gas with a hot continuous source behind it - such as a star.. Therefore, when this light passes through a gas, the gas atoms may absorb certain wavelengths to produce a line absorption spectrum.
Black hydrogen absorption lines are at the same wavelength as the bright hydrogen emission lines.
Question
Use the atomic spectra to identify the unknown element.
Strontium. It has the same line spectra as the unknown element.
