The main difference between emission and absorption spectra is that an emission spectrum has different coloured lines in the spectrum, whereas an absorption spectrum has dark-coloured lines in the spectrum.

A hot gas only emits certain wavelengths of light to produce bright lines on a dark background. This is called a line emission spectrum 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.

There are two types of line spectra, emission and absorption. In an emission spectra electrons are excited to an excited state by thermal or electrical means and then relax back to a lower state and emit a photon of light at a specific energy, which is seen as at a specific wavelength.

The emission spectrum is the spectrum of radiation emitted by a substance that has absorbed energy. Atoms, molecules, and ions that have absorbed radiation are called ‘ excited ‘. The absorption spectrum is the opposite of the emission spectrum.

An absorption spectrum has dark lines or gaps in the spectrum corresponding to wavelengths that are absorbed by the gas. Emission Spectrum: Starlight can also heat up a cloud of gas, exciting the atoms and molecules within the gas, and causing it to emit light.