The green light emitted from europium falls within which wavelength range?

• A. 100-200 nm
• B. 600-700 nm
• C. 300-500 nm
• D. 800-900 nm

Answer: (C)

Europium’s emission color depends on its oxidation state. In the +2 state, europium gives a broad blue-green emission centered around 490 nm, which sits in the 300–500 nm range. That’s the portion of the spectrum where green light lies. The other ranges correspond to ultraviolet (100–200 nm), red visible light (600–700 nm), and infrared (800–900 nm), so they don’t match the green emission. Thus, the green light from europium falls within 300–500 nm.