# Gross hydrogen emission spectrum

One reasonable and memorable approximation excluding any fine structure is: $$Equation 1. Hydrogen spectral series mnemonic En​=−n213.6eV​ (1)$$ see for example example: hydrogen 1-2 spectral line.

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

Equation "Hydrogen spectral series mnemonic" gives for example from principal quantum number 1 to 2 a difference: $$En​=−13.6eV[221​−121​]=10.2eV (1)$$ which with Planck-Einstein relation gives about 121.6 nm ( Hz), which is a reasonable match with the value of 121.567... from the NIST Atomic Spectra Database.