Question

Up-vis adsorption spectra are broad band spectra. Explain

Answer 1

Electronic excitations are usually accompanied by vibrational
transitions which are usually not resolved. As a consequence
broad bands result. This is pretty much the same situation as if
you investigate the infrared spectra of gases. In this case,
vibrational excitations are accompanied by rotational transitions. If
your spectrometer is not able to resolve the individual bands, also
comparably broad bands result. On the other hand, if you have
liquids or solids, these rotational transitions are no longer possible
and you see solely the band of the vibrational transition.