Question

Given below are two statements:
Assertion (A): The angle between any two faces of a crystal is termed as interfacial angle.
Reason (R): The interfacial angles of corresponding faces of different crystals are constant if they have same chemical composition and measurements are taken at same temperature.

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is not the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Interfacial angles remain constant for corresponding faces of crystals of the same substance.

Answer 1

The Correct Option is B

Concept:
Interfacial angle is an important crystallographic property used in crystal identification.

Step 1: Check Assertion.
The angle between two crystal faces is called the interfacial angle. \[ A \text{ is correct} \]

Step 2: Check Reason.
According to the law of constancy of interfacial angles, corresponding faces of crystals of the same substance show constant angles under the same conditions. \[ R \text{ is correct} \]

Step 3: Check explanation.
Reason states an important law about interfacial angles, but it does not define why the angle between two faces is called interfacial angle. \[ R \text{ is not the correct explanation of } A \] \[ \therefore \text{Correct Answer is (B)} \]