Which of the following is correct?

Options

A. AgBr shows both Schottky and Frankel defect
B. Frenkel defect is shown by ionic solids where there is large difference in size of anioun and cation
C. In Frankel defect, dielectric constant of crystal increases
D. All are correct

Answer

To determine which of the given statements is correct, we will analyze each option related to defects in solids, specifically focusing on Schottky and Frenkel defects.

### Step-by-Step Solution:

1. **Understanding Schottky Defect**:
- Schottky defect occurs when some ions are completely missing from the lattice structure of a crystal. This results in a decrease in the density of the crystal.
- Example: AgBr (Silver Bromide) is known to exhibit Schottky defects.

**Hint**: Remember that Schottky defects involve missing ions, leading to a decrease in density.

2. **Understanding Frenkel Defect**:
- Frenkel defect occurs when ions or atoms are displaced from their normal lattice positions and occupy interstitial sites (voids) within the crystal structure. This defect does not significantly affect the density of the crystal.
- Example: Ionic solids with a large difference in size between cations and anions tend to exhibit Frenkel defects.

**Hint**: Frenkel defects involve displacement of ions to interstitial sites, not missing ions.

3. **Analyzing Each Statement**:
- **Statement 1**: "AGBr shows both Schottky and Frenkel defect."
- This statement is correct as AgBr can exhibit both types of defects.

- **Statement 2**: "Frenkel defect is shown by ionic solid where there is a large difference in size of anion and cation."
- This statement is also correct. Frenkel defects are typically observed in ionic solids with a significant size difference between cations and anions.

- **Statement 3**: "In Frenkel defect, dielectric constant of crystal increases."
- This statement is correct as well. The displacement of ions in Frenkel defects leads to a closer arrangement of charges, which increases the dielectric constant of the crystal.

- **Statement 4**: "All of the following are correct."
- Since the first three statements are correct, this statement is also true.

4. **Conclusion**:
- All the statements provided in the options are correct. Therefore, the correct answer is **Option 4: All of the following are correct.**

### Final Answer:
**Option 4: All of the following are correct.**