Question

How does a line spectrum differ from a continuous spectrum? Why does an atom produce a line spectrum rather than continuous spectrum when energy is added to the atom?

Answer 1

There are two main types of spectras - Line spectrum and continuous spectrum.

Line spectrum is either an absorption spectrum or emission spectrum whereas continuous spectrum is the superimposed image of both absorption and emission spectrum.Thus, line spectrum consists of only a few wavelengths whereas continuous spectrum ususally contains all the wavelengths of a given range. There are huge gaps between lines in a line spectra whereas in a continuous spectra there are no observable gaps.

Example of a line spectra - emission spectra of hydrogen, Continuous spectra- Rainbow and black body radiation.

When an atom absorb energy or is hit by a photon of light, it absorbs the quanta of energy and jumps to a higher energy state. Then, since atoms can only be in specific orbitals, these higher energy atoms give up the extra energy in the form of photon of light and fall back down to their original energy level.

This transition between levels produce a line spectrum.