| fluorescence spectrum | Fluorescence evoked over a range of wavelengths when the excitation wavelength is at a maximum. (05 Mar 2000) |
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| fortification spectrum | The zigzag banding of light, resembling the walls of fortified medieval towns, that marks the margin of the scintillating scotoma of migraine. Synonym: fortification figures, telehopsias. (05 Mar 2000) |
| frequency spectrum | The range of frequencies in a signal, used to describe the resolving power of an imaging system in radiology. (05 Mar 2000) |