IGNOU MPHE 25 2026 - What is F centre defect? Why is there a characteristic absorption ener

Question

What is F centre defect? Why is there a characteristic absorption energy associated with the F centre? If the F centre absorption energy for CsCl is 2.0 eV, what is its characteristic absorption wavelength?

19 Jan 2026

Answer :

Word Count : 293

An F center defect, also called a color center, is a type of point defect in an ionic crystal in which an anion vacancy is occupied by one or more electrons. In simple terms, it occurs when a negatively charged ion is missing from its lattice site, and the resulting vacancy traps an electron. This trapped electron can interact with light, leading

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