# What is a dihedral mirror plane?

The

**dihedral**(or diagonal)**mirror plane**reflection. The**mirror plane**contains a principal axis and bisects the angle between two horizontal axes. (These horizontal axes are perpendicular to the principal axis.) The operator reflects the object across the**plane**of symmetry.A.

### What is Sigma D plane?

A

**plane**that cuts through a molecule in a way that images of all the molecule's features beyond the**plane**seem to produce an identical molecule is a mirror**plane**or a**plane**of reflection. The corresponding operation as well as the**plane**as symmetry element are denoted with the greek letter σ.#### What is inversion symmetry?

A**symmetry**plane can also be identified by its Cartesian orientation, e.g., (xz) or (yz). Center of**symmetry**or**inversion**center, abbreviated i. A molecule has a center of**symmetry**when, for any atom in the molecule, an identical atom exists diametrically opposite this center an equal distance from it.#### What is the definition of axis of symmetry?

A line of**symmetry**for a graph. The two sides of a graph on either side of the**axis**of**symmetry**look like mirror images of each other. Example: This is a graph of the parabola y = x^{2}– 4x + 2 together with its**axis**of**symmetry**x = 2. The**axis**of**symmetry**is the red vertical line.#### What is a dihedral reflection plane?

The**dihedral**(or diagonal)**mirror plane reflection**. The**mirror plane**contains a principal axis and bisects the angle between two horizontal axes. (These horizontal axes are perpendicular to the principal axis.) The operator reflects the object across the**plane**of symmetry.

B.

### What is an improper axis of rotation?

In geometry, an

**improper rotation**, also called rotoreflection, rotary reflection, or rotoinversion is, depending on context, a linear transformation or affine transformation which is the combination of a**rotation**about an axis and a reflection in a plane perpendicular to that axis.#### Is the Earth closer or farther from the sun during winter?

Because the**earth's**axis is tilted. It is all about the tilt of the**Earth's**axis. Many people believe that the temperature changes because the**Earth**is**closer**to the**sun**in**summer**and**farther from the sun**in**winter**. In fact, the**Earth**is**farthest from the sun**in July and is closest to the**sun**in January!#### What is the closest black hole to Earth?

The**closest black holes**yet discovered are several thousand light-years away. They are so far that they have no effect on**Earth**or its environment. A supermassive**black hole**appears to inhabit the center of the Milky Way galaxy, about 27,000 light-years away.#### Can you destroy a black hole?

Since nothing**can**escape from the gravitational force of a**black hole**, it was long thought that**black holes**are impossible to**destroy**. But**we**now know that**black holes**actually evaporate, slowly returning their energy to the Universe.

C.

### What are the elements of symmetry?

A symmetry element is a point of reference about which symmetry

**operations**can take place. In particular, symmetry elements can be identities, mirror planes, axes of rotation (both proper and improper), and centers of inversion.#### What is alternating axis of symmetry?

**Alternate axis of symmetry**is the line passing through the molecular structure around which if rotated through an angle X followed by reflection on a mirror placed at right angle to the**axis**produces the same face of the molecule. Such an**alternating axis**will be called C4**axis of symmetry**.#### What is a c2 axis of symmetry?

**Symmetry**Operations: Rotation. The red**axis**is an**axis of symmetry**of A. The operation of rotation (Cn) involves rotation. of the molecule 360/n degrees about an**axis**. The**axis**shown is a “**C2**”**axis**.#### What does it mean to be Achiral?

Definitions:**Achiral**. A molecule**is achiral**if it**is**superimposable on its mirror image. Most**achiral**molecules**do**have a plane of symmetry or a center of symmetry.**Achiral**molecules that contain a stereocenter**are**called meso.

Updated: 18th November 2019