What does the presence of dark lines in the line absorption spectrum signify?

The presence of dark lines in the line absorption spectrum signifies specific wavelengths of light that were absorbed by a substance. When light passes through a cool, gaseous medium, certain wavelengths corresponding to the energy levels of the atoms or molecules in that medium are absorbed. This absorption occurs because electrons in the atoms or molecules take in energy, allowing them to move from a lower energy level to a higher one. The absorbed wavelengths are removed from the spectrum of the transmitted light, resulting in dark lines at those specific wavelengths.

This phenomenon is critical in spectroscopy, as it allows scientists to identify the composition of distant stars and gases by matching the dark lines observed in their spectra to known absorption lines of elements. Each element has a unique set of energy levels, and thus, a unique set of absorption lines, making it possible to discern the presence of various elements based on the specific wavelengths that are missing from the spectrum.

The other options reflect different aspects of spectral analysis but do not accurately describe the significance of dark lines in an absorption spectrum. Emitted wavelengths correspond to bright lines in emission spectra, while the presence of multiple elements may lead to additional lines but not specifically dark lines. Temperature variations can affect the intensity and broadening of lines but are not the direct cause of