Excited states do not in general live very long before they decay.Suppose a certain excited state lives just 10^-7 s. In that case weknow the time when the atom is in the excited state quiteaccurately--to within ?t=10^-7 s. That means there is a significantuncertainty ?E in the energy of the state.
(a) (i got this part) estimate the size of this uncertainty.Answer: ?E=6.63x10^-23
(b) Hence estimate the range ?f of frequencies that will bemeasured for the photons given off when the state decays.
(c) A particular spectral line in hydrogen has wavelengthλ=121.5 nm and is observed to have a line width (in terms ofwavelength) of about 10^-7 λ. Estimate the lifetime of the corresponding excited state.