# (S-5) Waves and Photons

This lesson introduces students to electromagnetic waves, at a qualitative high-school level. It then brings up the concept of photons, and the relation between photon wavelength and energy. This is tied to solar observations at various wavelengths.

Part of a high school course on astronomy, Newtonian mechanics and spaceflight
by David P. Stern

 This lesson plan supplements: "Waves and Photons," section #S-5: on disk Sun5wave.htm, on the web           http://www.phy6.org/stargaze/Sun5wave.htm "From Stargazers to Starships" home page and index: on disk Sintro.htm, on the web           http://www.phy6.org/stargaze/Sintro.htm

 Goals: The student will learn About the many types of electromagnetic waves, and about observing the Sun using different members of that family. Qualitatively, about the concept of an electromagnetic (EM) wave, as a linked oscillation of magnetic fields and electric currents, spreading through space. How James Clerk Maxwell proposed a slight modification of the equations of electricity, under which electromagnetic (EM) waves could exist, and how he identified light as such a wave, after which Heinrich Hertz created radio-frequency EM waves in his lab, the beginning of research with radio waves. That although light spreads like a wave, it only gives up its energy in well-defined amounts, known as photons. That the shorter the wavelength, the bigger the photon energy. Thus hot regions of the Sun, whose atoms move faster and therefore have more energy, are likely to emit shorter wavelengths. That light is also emitted in photons. When an individual atom emits light, it usually changes from some "excited state" of higher energy to one with lower energy. The energy (and hence, color) of the emitted photon is very precisely determined by the difference between those levels. Terms: wave, electromagnetic wave, wavelength, wave velocity, frequency, photon, Planck's constant, (atomic) energy level, excited atom, solar prominences. Stories: The discovery of electromagnetic waves. This lesson plan also includes (optional) the story of whistlers and a brief comment on laser action.