Absorption spectroscopy exercises

The light passing through a cloud of gas 300 light years from Earth is analysed. The spectrum of this light as well as the emission spectra for sulfur, zinc and helium are shown below. Which of the three elements are present in the cloud.

Below are the emission and absorption spectra of copper. One is a series of black lines on a coloured background while the other is a set of coloured lines on black background. Account for the difference in appearance of the two spectra. Account for the identical positioning of the lines in the two spectra.

To produce an absorption spectrum light is absorbed to promote the electron to a higher level and then released as the electron returns to its original energy level. Since energy is absorbed and then released, why do we have dark lines appearing in the spectrum? Hint

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