Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Plasma oscillations, also known as "Langmuir waves" (after Irving Langmuir), are rapid oscillations of the electron density in conducting media such as plasmas or metals. The frequency only depends weakly on the wavelength. The quasiparticle resulting from the quantization of these oscillations is the plasmonLangmuir waves were discovered by American physicists Irving Langmuir and Lewi Tonks in the 1920s. They are parallel in form to Jeans instability waves, which are caused by gravitational instabilities in a static medium.