CPC G01J 1/58 (2013.01) | 20 Claims |
1. A marker arranged to indicate the presence of ultraviolet radiation, the marker comprising at least an emitting layer having a fluorescent material arranged to emit visible light in a first range of wavelengths in response to excitation by ultraviolet radiation in a second range of wavelengths, the emission of visible light being reversible and the marker being reusable.
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