# Finite width of spectral emission lines [duplicate]

Photons nay be emitted from hydrogen at, say 656.28 nm but, I guess in accordance with time-frequency uncertainty, the emission spectrum has a small finite width. This finite width can be wider for emission spectra with shorter decay times, if my understanding is correct.

Spectral emissions are usually given as very precise frequencies. Are these approximations?

## marked as duplicate by stafusa, Kyle Kanos, Community♦Jan 17 at 13:24

• Uncertainty gives that $\Delta f\Delta t \geq k.$ If you have a handle on $\Delta f...$ – daniel Apr 30 '17 at 19:49