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Table I. Calculated wavelengths of nine observed lines of helium spectrum compared with wavelengths of visible transitions found on the helium energy-level diagram.
1 Μαρ 1998 · When observing the spectrum of helium in an introductory physics laboratory, a complete and satisfactory laboratory experience that provides insight into the connection between the observed wavelengths and the structure of the atom, is more difficult to achieve than when observing hydrogen.
Atomic Spectra. At left is a helium spectral tube excited by means of a 5000 volt transformer. At the right of the image are the spectral lines through a 600 line/mm diffraction grating. The nitrogen spectrum shown above shows distinct bands throughout the visible range.
The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur , India.
A matching absorption spectrum occurs when light passes through a material and is absorbed by its atoms. The 12 lines of the visible helium spectrum correspond to wavelengths of 388.8, 447.1, 471.3, 492.1, 501.5, 504.7, 587.5, 667.8, 686.7, 706.5, 728.1 and 781.3 nanometres (nm).
Atoms of individual elements emit light at only specific wavelengths, producing a line spectrum rather than the continuous spectrum of all wavelengths produced by a hot object. Niels Bohr explained the line spectrum of the hydrogen atom by assuming that the electron moved in circular orbits and that orbits with only certain radii were allowed.
1 Μαΐ 2016 · The spectral lines calculated, namely the specific wavelengths of light emitted by elements when they are energized, correspond to an assumed possible scenario where the two electrons make orbital transitions in unison. In this model we calculate an energy prediction for the unionized helium atom.
