Bright and dark line spectra

The origin of spectroscopy lies in the spectral analytical work of Thomas Melville, already described above, and the development of the spectroscope by William Wollaston and Josef Fraunhofer (1787-1826) (see Fig. 3.23). Melvilles s observation in 1752 that the spectrum of light of a flame passed through a prism was not continuous like that of the Sun, but rather that parts of the spectrum were bright, while others were dark, with the locations of the bright spots and their 

University of Chicago Press, Chicago (1987). i ibid., pp. 80 81. 

The Fraunhofer s spectroscope was constructed to receive light that had been passed through a slit and a tube to create a narrow beam, resulting in a spectrum beyond the prism that was then viewed through a telescope. This instrument allowed Fraunhofer to construct for the first time a map of the dark line spectra from the Sun, the principal lines from which he named with the letters A through G—the now-familiar Fraunhofer lines. In 1814—1815, he published his Sun and stellar studies that gave spectral analysis a real boost. 

The Great Physicists from Galileo to Einstein, p. 123, Dover Publications, New York (1961). 

Kirchhoff also formulated the law that now hears his name—Kirchhoff s law— which states that all substances ahsorh the same light frequencies that they can emit. This law has found widespread application in the study of composition of 

---