Question

Arrange the following features of a glass surface in the order of their appearance as a crack progresses from its origin. A. Hackle
B. Mist
C. Mirror
D. Conchoidal marks
Choose the correct answer from the options given below :

• A. C, B, A, D
• B. B, C, A, D
• C. C, A, B, D
• D. A, B, C, D

Hint:

Glass fracture order: Mirror (smooth) → Mist (cloudy) → Hackle (rough lines) → Conchoidal (curved marks).

Answer 1

The Correct Option is A

Concept: Fracture patterns in glass provide valuable forensic information regarding the origin and direction of force. When glass breaks, the crack propagates outward from the point of impact, producing distinct zones and markings in a sequential order.

Step 1: Understanding Mirror region.
The mirror region is the smooth, clear area immediately surrounding the point of impact. It is the first region formed when the crack initiates. It indicates the origin of fracture.
Thus, Mirror appears first.

Step 2: Understanding Mist region.
As the crack propagates further, the surface becomes slightly rougher, forming the mist region. This area shows a cloudy appearance due to increased fracture velocity.
Thus, Mist appears after the mirror region.

Step 3: Understanding Hackle marks.
Hackle marks are rough, ribbed patterns that appear as the crack continues to spread rapidly. These marks indicate the direction of crack propagation.
Thus, Hackle appears after mist.

Step 4: Understanding Conchoidal marks.
Conchoidal marks are curved fracture patterns typically formed at later stages when the crack energy disperses further. These are not immediate but appear as the fracture extends.
Thus, Conchoidal marks appear last.

Step 5: Forming correct sequence.
\[ \text{Mirror} \rightarrow \text{Mist} \rightarrow \text{Hackle} \rightarrow \text{Conchoidal marks} \] \[ C \rightarrow B \rightarrow A \rightarrow D \] Final Conclusion:
Hence, the correct answer is (1).