Which term best describes the emission of visible light by a material when it is exposed to ultraviolet light?

Which term best describes the emission of visible light by a material when it is exposed to ultraviolet light?

• A. Metamerism
• B. Gamma phase
• C. Opalescence
• D. Fluorescence

Answer: (D)

Fluorescence is the emission of visible light by a substance when it absorbs ultraviolet light. When UV photons hit the material, electrons are excited to higher energy levels. As they return to lower levels, they release energy as photons in the visible range, causing the material to glow while the UV light is present. This glow stops almost immediately when the UV source is removed, unlike phosphorescence which can persist after the excitation ends. The other terms don’t describe this effect: metamerism relates to color perception under different lights, opalescence is a milky, scattering effect, and gamma phase isn’t the phenomenon described here.

Fluorescence is the emission of visible light by a substance when it absorbs ultraviolet light. When UV photons hit the material, electrons are excited to higher energy levels. As they return to lower levels, they release energy as photons in the visible range, causing the material to glow while the UV light is present. This glow stops almost immediately when the UV source is removed, unlike phosphorescence which can persist after the excitation ends. The other terms don’t describe this effect: metamerism relates to color perception under different lights, opalescence is a milky, scattering effect, and gamma phase isn’t the phenomenon described here.