Which Compound is known as night glowing pigment from below?

Question

Which Compound is known as night glowing pigment from below?

1. A. Europium dopped strontium aluminate (Correct answer)
2. B. Copper Sulphide dopped zinc oxide
3. C. Barium sulphate dopped copper carbonate
4. D. Boron oxide dopped copper sulphate

Correct Answer

Option A — Europium dopped strontium aluminate

Detailed Solution & Explanation

The correct answer is Europium dopped strontium aluminate.

Key Points

• Strontium aluminate doped with europium — written as SrAl₂O₄:Eu²⁺, Dy³⁺ — is the compound widely known as a night-glowing or glow-in-the-dark pigment.
• It works by phosphorescence: the material absorbs and stores energy from ambient light, and then re-emits that energy slowly as visible light over several hours. Europium acts as the activator that produces the characteristic green emission, while dysprosium serves as a co-dopant that traps electrons and greatly prolongs the afterglow.
• This pigment largely replaced the older zinc sulphide and the hazardous radium-based luminous paints.
• Its practical applications include emergency exit signage, safety markings, watch dials, road studs and toys, because it requires no power source.

Exam Tip

• distinguish fluorescence (emission stops the instant the exciting light is removed) from phosphorescence (emission continues for a period afterwards) — this conceptual difference is the usual second layer of such questions.

प्रश्न (हिन्दी में)

नीचे से रात में चमकने वाले वर्णक के रूप में कौन–सा यौगिक जाना जाता है?

1. A. यूरोपियम डोप्ड स्ट्रॉन्टियम एलुमिनेट
2. B. कॉपर सल्फाइड डोप्ड जिंक ऑक्साइड
3. C. बेरियम सल्फेट डोप्ड कॉपर कार्बोनेट
4. D. बोरॉन ऑक्साइड डोप्ड कॉपर सल्फेट