Question

The two-dimensional defect is

• A. Grain boundary defect
• B. Point defect
• C. Line defect
• D. Volume defect

Hint:

Remember: Grain boundaries are surface defects and hence classified as two-dimensional defects.

Answer 1

The Correct Option is A

Step 1: Classification of crystal defects.
Crystal defects are categorized based on their dimensionality: zero-dimensional (point defects), one-dimensional (line defects), two-dimensional (surface defects), and three-dimensional (volume defects).
Step 2: Understanding grain boundaries.
Grain boundaries are interfaces between two crystals of different orientations. Since they extend over an area, they are considered two-dimensional defects.
Step 3: Analysis of other options.
(B) Point defect: Zero-dimensional defects such as vacancies.
(C) Line defect: One-dimensional defects like dislocations.
(D) Volume defect: Three-dimensional defects such as voids and inclusions.
Step 4: Conclusion.
Therefore, grain boundary defect is a two-dimensional defect.