Final answer:
The bright-line spectrum of an element is produced when electrons transition from higher to lower energy levels, releasing photons that correspond to specific wavelengths.
Step-by-step explanation:
The characteristic bright-line spectrum of an element occurs when electrons move from higher to lower energy levels. This transition releases energy in the form of photons, resulting in the emission of light at specific wavelengths unique to each element, known as the atomic emission spectrum. Niels Bohr's model explained these bright lines as being the result of electrons dropping from excited states to lower energy orbits, releasing a photon for each transition.
The different energy levels available to the electrons in an atom are quantized, leading to discrete spectral lines. These spectra can be used to identify elements in various materials, including stars and interstellar gas.