Question

Which of the following statements is/are true for hemihedral forms?
A. They belong to the same crystal class as the holohedral forms,
B. They have the same indices as the holohedral form,
C. They have half number of faces as the holohedral form,
D. For each holohedral form these correspond to two hemihedral forms. Choose the correct answer from the options given below:

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

Hint:

Hemihedral forms have half the number of faces of the corresponding holohedral form.

Answer 1

The Correct Option is D

Concept:
Hemihedral forms are crystal forms having half the number of faces compared to the corresponding holohedral form.

Step 1: Check statement A.
Hemihedral forms do not represent the same full symmetry condition as holohedral forms. \[ A \text{ is not selected} \]

Step 2: Check statement B.
Hemihedral forms can have the same indices as the corresponding holohedral form. \[ B \text{ is correct} \]

Step 3: Check statement C.
By definition, hemihedral forms have half the number of faces of the holohedral form. \[ C \text{ is correct} \]

Step 4: Check statement D.
For a holohedral form, two corresponding hemihedral forms may occur. \[ D \text{ is correct} \] Therefore, the correct statements are: \[ B,C,D \] \[ \therefore \text{Correct Answer is (D)} \]