Why do lines get closer in line spectrum?

Lines in a line spectrum get closer together due to the quantization of energy levels in an atom. As the energy levels become more closely spaced at higher energy states, the emitted or absorbed light corresponds to these transitions, resulting in spectral lines that are closer to each other. This effect is particularly noticeable in elements with many electrons, where the interactions between electrons lead to complex splitting of energy levels. Consequently, the resulting spectrum shows a denser arrangement of lines at higher frequencies or energies.