The visible light has a wavelength range from about 380 nm (violet) to 780 nm (red). If an excited object emits light with wavelength of 15 nm, to which one of the following ranges does it belongs?

The electromagnetic spectrum is categorized by wavelength, with visible light occupying a narrow band between approximately 380 nm and 780 nm [t3][t5]. Radiation with wavelengths longer than 780 nm is classified as infrared [t8]. Conversely, radiation with wavelengths shorter than the visible violet end (below 380 nm) is classified as ultraviolet (UV) radiation [t1][t9]. Specifically, the ultraviolet range is defined as spanning from 10 nm to 400 nm, situated between X-rays and visible light [t1][t10]. X-rays typically occupy the range from 0.01 nm to 10 nm, while gamma rays have even shorter wavelengths, generally less than 0.01 nm [t1][t6]. Since the object in the question emits light at 15 nm, it falls squarely within the 10 nm to 400 nm range designated for ultraviolet radiation [t1][t10].

Sources

1. [1] https://publications.iarc.who.int/_publications/media/download/1890/ca611a178e36ddb0dc5a1dacc63bb5a99925b09e.pdf
2. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC9938358/