The series limit of a spectral series corresponds to a transition from

  • A. the next level up
  • B. n equals infinity, that is from a free electron
  • C. the ground state
  • D. a level below the final one

Explanation

As the starting level rises the lines crowd together and converge on a shortest wavelength, which corresponds to an electron falling from infinity, that is from the point of ionisation. Measuring the Lyman series limit therefore gives the ionisation energy of hydrogen directly. Beyond the limit the spectrum becomes continuous.

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