Hydrogen 1-2 spectral line (121.6 nm, 10.2e V)

Equation 2. "Hydrogen spectral series mnemonic" gives for example from principal quantum number 1 to 2 a difference: which with Planck-Einstein relation gives about 121.6 nm ($2.47\times 10^{1}5$ Hz), which is a reasonable match with the value of 121.567... from the NIST Atomic Spectra Database.