Question

Which one of the following defines a hexagonal dipyramid?

• A. A vertical six fold axis of symmetry
• B. A horizontal mirror plane
• C. Six vertical mirror planes at an angle of 30° with each other
• D. A mirror plane that is perpendicular to the vertical six fold axis of symmetry

Hint:

A hexagonal dipyramid has six faces and a vertical six-fold axis of symmetry.

Answer 1

The Correct Option is D

Step 1: Understanding a hexagonal dipyramid.
A hexagonal dipyramid is a type of polyhedron that has six triangular faces and a vertical six-fold axis of symmetry. It can be visualized as two pyramids joined at their bases, with the symmetry axis passing vertically through the center.

Step 2: Analyzing the options.
(A) A vertical six fold axis of symmetry: Correct — This defines the symmetry of a hexagonal dipyramid.
(B) A horizontal mirror plane: This does not describe a hexagonal dipyramid.
(C) Six vertical mirror planes at an angle of 30° with each other: This option does not describe the symmetry of a hexagonal dipyramid.
(D) A mirror plane that is perpendicular to the vertical six fold axis of symmetry: This is not the defining characteristic of a hexagonal dipyramid.

Step 3: Conclusion.
The correct answer is (A) A vertical six fold axis of symmetry, as this is the key characteristic of a hexagonal dipyramid.