Opposite to Ultraviolet on the Light Spectrum
Puzzle 6 of Deserts Medium Pack
Question is: Opposite to Ultraviolet on the Light Spectrum
and the answer is: INFRARED
Word Meaning:
INFRARED — (uncountable) The electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation, having a wavelength between 700 nm and 1 mm.
Definitions from Wiktionary.