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State PCS PYQPrelims 2025

BPSC – Combined Competitive Examination · প্রশ্ন 132

Which compound is known as a glow-in-the-dark (night glowing) pigment?

Europium-doped strontium aluminate
Copper sulphide-doped zinc oxide
Barium sulphate-doped copper carbonate
Boron oxide-doped copper sulphate

উত্তর দেখান ও ব্যাখ্যা

উত্তর: (A) Europium-doped strontium aluminate

ব্যাখ্যা

Europium (and dysprosium) doped strontium aluminate glows for hours after charging with light.

(A) সঠিক
Correct: SrAl₂O₄:Eu is the main long-afterglow phosphor.
(B) ভুল
Wrong: the older phosphor was copper-doped zinc sulphide, not this.
(C) ভুল
Wrong: not a luminous pigment.
(D) ভুল
Wrong: not a luminous pigment.