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| abstraction > mathematical concept > number > quantity > radiation measurement > spectral feature > spectral line > absorption line > Fraunhofer line > HK lines > Ca H line |
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| Ca H line comparison table | |||
| Subject | has definition | is a kind of | has wavelength |
|---|---|---|---|
| HK lines | Two spectral lines of singly ionized calcium. The second strongest interstellar line. | Fraunhofer line | |
| Ca H line | A spectral line of singly ionized calcium. | HK lines | 3968 Å |