Question

Which of the following is/are incorrect for humphrey lines of the hydrogen spectrum?
\[\begin{array}{*{20}{l}}
  {A:{\text{ }}{n_2} = {\text{ }}7 \to {n_1} = {\text{ }}2} \\
  {B:{\text{ }}{n_2} = {\text{ }}10 \to {n_1} = {\text{ }}6} \\
  {C:{\text{ }}{n_2} = {\text{ }}5 \to {n_1} = {\text{ }}1} \\
  {D:{\text{ }}{n_2} = {\text{ }}11 \to {n_1} = {\text{ }}3}
\end{array}\]

Answer 1

Hint: Observing and recording the wavelengths of the emitted photons results in an emission spectrum consisting of discrete lines. And lines in the hydrogen emission spectrum are combined grouped together in a number of different series. Each of these series further correspond to the excited electrons falling down to a particular energy level.

Complete step by step answer:
The Humphrey series of hydrogen spectrum was first observed in 1953, by an American Physicist named Curtis J Humphreys. Therefore, this series is named after his name. The Humphrey lines of the hydrogen spectrum is shown when the electron transition occurs from higher energy states, $n_2$ =7,8,9,10…) to $n_1$ =6 energy state. All the wavelengths of Humphreys lines lie in the Infrared region of the electromagnetic spectrum. Different names are employed for different lines of the hydrogen spectrum as displayed below:
For:
\[
  \begin{array}{*{20}{l}}
  {\;{n_1} = 1:\;Lyman{\text{ }}series}
  {{n_1} = 2:\;Balmer{\text{ }}series}
  {{n_1} = 3:\;Paschen{\text{ }}series}
  {{n_1} = 4:\;Brackett{\text{ }}series}
  {{n_1} = 5:\;Pfund{\text{ }}series}
\end{array}
  {n_{1}} = {\text{ }}6:\;Humphrey{\text{ }}series
\]
Now for every option given in the question, where \[n \ne 6\;\]is the incorrect option.

Thus, correct options are A, C and D.

Note: Humphrey lines refer to the series of lines in the hydrogen spectrum possessing the form: $\dfrac{1}{\lambda } = R\left( {\dfrac{1}{{{6^2}}} - \dfrac{1}{{{n^2}}}} \right),n = 7,8,9...$, where $\lambda$ refers to the wavelength linked with the lines and on the other hand, R refers to the Rydberg constant.