Fluorescent materials glow under ultraviolet light because they
Correct answer: B. absorb ultraviolet photons and re-emit the energy as several lower energy visible photons
- A. reflect ultraviolet light
- B. absorb ultraviolet photons and re-emit the energy as several lower energy visible photons
- C. become hot
- D. emit ultraviolet light of their own
Explanation
The absorbed photon lifts an electron high, and it returns in smaller steps, so the emitted photons have less energy and longer wavelength, which shifts the light into the visible range. This is exactly how the coating inside a fluorescent tube converts the ultraviolet from the mercury discharge into white light. Phosphorescence is the same process with a delay of seconds or longer.
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About Atomic Spectra
Atoms emit or absorb light at specific wavelengths because electrons occupy quantized energy levels and change levels by absorbing or releasing photons. The topic covers emission and absorption spectra, spectral series, hydrogen’s line spectrum, energy-level transitions, and the relation between wavelength, frequency and photon energy.
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