Light of wavelength $0.6 \mu \mathrm{m}(6000 \mathrm{~A})$ is emitted by an electron in an atom behaving as a lightly damped simple harmonic oscillator with a $Q$ -value of $5 \times 10^{7}$. Show from the resonance bandwidth that the width of the spectral line from such an atom is $1.2 \times 10^{-14} \mathrm{~m}$.