Meaning of SPECTRUM in English
( n. )
A luminous appearance, or an image seen after the eye has been exposed to an intense light or a strongly illuminated object. When the object is colored, the image appears of the complementary color, as a green image seen after viewing a red wafer lying on white paper. Called also ocular spectrum.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012