Science, Tech, Math › Science Spectrum Definition in Chemistry Share Flipboard Email Print A spectrum is a set of wavelengths of light or electromagnetic radiation. Getty Images/LAWRENCE LAWRY/SCIENCE PHOTO LIBRARY Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 03, 2019 A spectrum is defined as the characteristic wavelengths of electromagnetic radiation (or a portion thereof) that is emitted or absorbed by an object or substance, atom, or molecule. Plural: Spectra Example Examples of a spectrum include the rainbow, the emission colors from the Sun, and the infrared absorption wavelengths from a molecule.