SpectraAstronomy 1401 - OnlineThe purpose of this laboratory activity is to examine the atomic spectra given off from excited gasesand identify an element by its spectra.Part 1: BackgroundEmission SpectraWhen an atom is excited (i.e., when it absorbs energy), electrons change their energy levels to higherones. When electrons from higher energy levels drop back down to lower energy levels, energy i
Astronomy 1401 - Online
The purpose of this laboratory activity is to examine the atomic spectra given off from excited gases
and identify an element by its spectra.
Part 1: Background
When an atom is excited (i.e., when it absorbs energy), electrons change their energy levels to higher
ones. When electrons from higher energy levels drop back down to lower energy levels, energy is
released in the form of light as shown in the Figure 1.1. The frequency of the emitted light depends
directly on the energy between the higher and the lower energy levels, and this determines the color of
the light. That is, the potential energy that is lost by the atom as its electron goes from a higher level to a
lower level, is converted into radiation (light). Thus from conservation of energy, we have that the
energy lost by the atom must equal exactly the energy of the photon emitted.
Every element has a unique spectrum of light composed of a set number of different frequencies
(called the “lines” of the spectrum; see Figure 1.2 for the case of hydrogen); if the atoms of a material
are excited (given energy, e.g. by heating), the elemental composition can be determined by resolving
those unique spectra from the emitted light