The color of metal ions in flame is due to which of the following?

Explain the following term with a suitable example:
$(iv)$ $F$-centres

Schottky defect defines imperfection in the lattice structure of a

Which of the following statements is $WRONG$?

Given below are two statements.
Statement $I:$ Frenkel defects are vacancy as well as interstitial defects.
Statement $II:$ Frenkel defect leads to colour in ionic solids due to presence of $F$-centres.
Choose the most appropriate answer for the statements from the options given below:

When $ZnO$ is heated,it turns from white to yellow because it ................