<p align="right">Last Update: <font color="#4f81bd">November, 25, 2024</font></p> ## BIG IDEAS - The spectrum of [[Electromagnetic radiation|electromagnetic radiation]] emitted or absorbed by an electron during transitions between different energy levels within an atom. - Spectra may be **line spectra**, **band spectra**, or **continuous spectra**. - Useful to determine elements of the sun. --- **Spectroscopy** is the study of emitted or absorbed electromagnetic radiation; it is a study of line spectra. ### Instrument A **spectrograph** is a tool producing dispersion, in which the spectrum is photographed. ### Types of Spectra There are two types of spectra: **emission** and **absorption**. - Emission spectra is observed when energy travels from the source to the observer. - Absorption spectra is observed when a portion of emitted energy is absorbed by an intervening medium. Spectral Lines Can be measured with great precision (up to 8 significant figures). Distance of the light source is independent #### Guiding Question: How do I identify that each element has a unique emission and absorption spectrum? Line spectrum - A glass tube filled with pure atomic gas. - Low pressure - Current is produced by a high potential difference applied between metal electrodes. - The tube gives off color. - The color of light is characteristic of the gas in the tube. emission spectrum - When light is emitted, then it is passed through a prism. - Results in a series of bright lines. - Each line is a different wavelength. - This “series of lines” is the emission spectrum. absorption spectrum is light being absorbed by the atom (rather than emitted as above). - Black lines exist where the wavelengths are absorbed. - The black lines are called Fraunhofer lines #### Guiding Question: How do I explain how line spectra are evidence for transitions between discrete energy levels Energy and wavelength are related using the equation $E_n \ = -\frac{13.6 eV}{n^2} \ (n \ = \ 1,2,3, \dots)$ where $n$ is a non-negative integer. - The negative value is based on a baseline energy of zero when the electron is infinitely far from the atom. - The minimum energy to free an electron from an atom is referred to as its binding energy. - Only valid for atoms with single electrons in their orbital shells (e.g., hydrogen). ### Related Topics --- [[Home|Home]] | [[Quantum mechanics]] | [[Notes Vault/Physics Notes Vault/Quantity of Motion/Quantum Mechanics/Blackbody Radiation|Blackbody Radiation]] | [[Photoelectric Effect]] | [[Atomic Theory]]