The appearance of colour in solid alkali metal halides is generally due to

Assertion: In an ionic solid $(MX)$,Schottky defect contains an equal number of cations and anions.
Reason: Equal number of vacancies are present for both cations and anions.

Which one of the following has Frenkel defect?

Which of the following statements are not correct?
$(A)$ Diode is a combination of $n$-type and $p$-type semiconductors.
$(B)$ Silicon or germanium is electron rich impurity.
$(C)$ Phosphorus and arsenic are electron deficient impurities.
$(D)$ Schottky defect decreases the density of the crystal.

The incorrect statement regarding defects in crystalline solid is

Identify the type of defect in brass alloy.