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| abstraction > mathematical concept > number > quantity > radiation measurement > spectral feature > spectral line > U line | 
| U line comparison table | ||||
| Subject | has specie | has definition | is a kind of | has wavelength | 
|---|---|---|---|---|
| spectral line | A line corresponding to an image of the entrance slit of the spectrometer, seen when light is either emitted by or interrupted by a hot rarefied gas such as hydrogen. The pattern is characteristic of the gas and the wavelength at which the features are observed to occur is indicative of the velocity of the object. | spectral feature | ||
| U line | sodium (Na I) | spectral line | 3302 Å | 
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