Consider the spectral line resulting from the transition n = 2 → n = 1 in the atoms and ions given below. The shortest wavelength is produced by

Step-by-step solution

Shortest wavelength will correspond to maximum energy. As the value of the atomic number ( Z ) increases, the magnitude of energy in different energy states gets increased. Value of Z is maximum for doubly ionised lithium atom ( Z = 3 ) among the given elements. Hence, the wavelength corresponding to this will be least.