Q. Which Compound is known as night glowing pigment from below?

Correct Answer: c) Europium dopped strontium aluminate

Explanation:
– “Night glowing” or “glow-in-the-dark” pigments are phosphorescent materials that store light and slowly release it in the dark.
– The most common and brightest modern glow pigments are based on strontium aluminate doped with europium (often with a co-dopant like dysprosium), e.g., SrAl2O4:Eu, Dy. They have a long-lasting, bright afterglow.
– The other options are not standard persistent phosphors:
– Barium sulfate is mostly an inert filler and not used this way.
– Copper sulphide doped zinc oxide is not the classic glow system (older ones used copper-doped zinc sulfide, ZnS:Cu).
– Boron oxide doped copper sulphate is not a known night-glow pigment.