Question

Which of the following statements are correct?
A. Defects in solids can affect the electrical property,
B. Defects in solids can affect the optical property,
C. Defects cannot be created by any technique,
D. Defects can be removed permanently with any technique.

• A. C and D Only
• B. A, B and C Only
• C. B and C Only
• D. A and B Only

Hint:

Defects strongly affect electrical, optical, mechanical and thermal properties of solids.

Answer 1

The Correct Option is D

Concept:
Defects in solids change the physical properties of materials. These defects may be point defects, line defects, surface defects or volume defects.

Step 1: Electrical property.
Defects can introduce energy levels and scattering centers in solids. Therefore, they can affect electrical conductivity. \[ A \text{ is correct} \]

Step 2: Optical property.
Defects can create colour centers and modify absorption or emission of light. \[ B \text{ is correct} \]

Step 3: Creation of defects.
Defects can be created by techniques such as irradiation, doping, quenching and mechanical deformation. \[ C \text{ is incorrect} \]

Step 4: Permanent removal of defects.
Some defects can be reduced by annealing, but defects cannot always be removed permanently by any technique. \[ D \text{ is incorrect} \] Therefore, correct statements are: \[ A,B \] \[ \therefore \text{Correct Answer is (D)} \]