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NEET levelSingle correct optionDifficulty 1 of 3ss186

An F-centre in an alkali halide crystal is

Aa cation vacancy occupied by a hole
Ban anion vacancy occupied by an unpaired electron
Ca pair of cation and anion vacancies
Dan interstitial cation

Answer: B

When an alkali halide is heated in alkali-metal vapour, halide ions vacate their sites and electrons from the metal atoms occupy these anion vacancies. These trapped electrons absorb visible light and give colour.

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