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  2. Hydrogen spectral series - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_spectral_series

    The spectral series of hydrogen, on a logarithmic scale. The emission spectrum of atomic hydrogen has been divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two energy levels in an atom.

  3. Hydrogen-alpha - Wikipedia

    en.wikipedia.org/wiki/Hydrogen-alpha

    Hydrogen-alpha, typically shortened to H-alpha or Hα, is a deep-red visible spectral line of the hydrogen atom with a wavelength of 656.28 nm in air and 656.46 nm in vacuum. It is the first spectral line in the Balmer series and is emitted when an electron falls from a hydrogen atom's third- to second-lowest energy level.

  4. List of counties in Pennsylvania - Wikipedia

    en.wikipedia.org/wiki/List_of_counties_in...

    The following is a list of the 67 counties of the U.S. state of Pennsylvania.The city of Philadelphia is coterminous with Philadelphia County, the municipalities having been consolidated in 1854, and all remaining county government functions having been merged into the city after a 1951 referendum.

  5. Balmer series - Wikipedia

    en.wikipedia.org/wiki/Balmer_series

    Balmer noticed that a single wavelength had a relation to every line in the hydrogen spectrum that was in the visible light region. That wavelength was 364.506 82 nm . When any integer higher than 2 was squared and then divided by itself squared minus 4, then that number multiplied by 364.506 82 nm (see equation below) gave the wavelength of ...

  6. Hydrogen line - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_line

    A hydrogen atom with proton and electron spins aligned (top) undergoes a flip of the electron spin, resulting in emission of a photon with a 21 cm wavelength (bottom) The hydrogen line, 21 centimeter line, or H I line [a] is a spectral line that is created by a change in the energy state of solitary, electrically neutral hydrogen atoms.

  7. H I region - Wikipedia

    en.wikipedia.org/wiki/H_I_region

    (H is the chemical symbol for hydrogen, and "I" is the Roman numeral. It is customary in astronomy to use the Roman numeral I for neutral atoms, II for singly-ionized—HII is H + in other sciences—III for doubly-ionized, e.g. OIII is O ++ , etc. [ 1 ] ) These regions do not emit detectable visible light (except in spectral lines from ...

  8. Pennsylvania Spatial Data Access - Wikipedia

    en.wikipedia.org/wiki/Pennsylvania_Spatial_Data...

    Pennsylvania Spatial Data Access (PASDA), [4] the official public geospatial data clearinghouse for the Commonwealth of Pennsylvania marked its 18th year in 2014. PASDA, which has grown from a small website offering 35 data sets in 1996 to the expansive user-centered data clearinghouse that it is today, has become a staple of the GIS community in Pennsylvania.

  9. File:Map of Pennsylvania highlighting Philadelphia County.svg

    en.wikipedia.org/wiki/File:Map_of_Pennsylvania...

    English: The maps use data from nationalatlas.gov, specifically countyp020.tar.gz on the Raw Data Download page. The maps also use state outline data from statesp020.tar.gz . The Florida maps use hydrogm020.tar.gz to display Lake Okeechobee.