= Spectral resolution
<Spectral resolution> describes the ability of a <spectrometer> to distinguish nearby <wavelengths> or <frequencies>. A common measure is the resolving power $R=\lambda/\Delta\lambda$, where $\Delta\lambda$ is the smallest wavelength separation distinguishable under a stated criterion.
At $\lambda=500\,\mathrm{nm}$, a resolving power of $10^4$ corresponds to $\Delta\lambda=0.05\,\mathrm{nm}$. A narrow atomic doublet may therefore appear as one feature in one instrument and as two lines in another. The instrument's response, source linewidth and <signal-to-noise ratio> all matter; detector sampling alone does not determine the true <spectral resolution>.
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