3b) What quantity distinguishes one series of lines from another?

Question

Account for the existence of several series of lines in the spectrum.

Answer 1

Lines occur because of how light is radiated and absorbed.

When a material is hot, it has a lot of energy. This energy can push an atom's electrons into a higher energy state. When that happens, the electron will eventually drop to a lower energy state. However, due to quantum principles, electrons can only exist at certain energy states. So, bright lines correspond to the energy differences between specific quantum states.

Similarly, dark lines occur when an atom absorbs a photon which pushes an electron from a lower to a higher state. It will only absorb photons that have the right energy to move between two legal quantum states. That will produce a dark line.

Answer 2

When electrons move from one energy level to another they either absorb energy (move higher) or lose energy (move lower). When they lose energy they lose it in the form of light. The energy released determines the frequency of the light; the frequency of the light determines the wavelength of the light. The wavelength determines which part of the light spectrum the light wave is in. So, the energy released is the quantity that ultimately determines which line and where.