Reflections
The first transformation that we will investigate is a reflection. A reflection in general terms is a flip on an object. A reflection is also known as the mirror image.
As described before, a reflection is a flip of an object. Typically the flip is over a line that is away from the object as shown below. This line is referred to as the line of reflection. You should notice that corresponding points such as A and A' are the same distance from the line of reflection.
Transformation Notation
There is a specific way to name a transformation. To describe this reflection in notation form we would say Figure ABCD --> Figure WXYZ. The important thing to remember is that you must have the corresponding vertices in the figures be in the same location in the notation.
For instance vertex A on the left diagram corresponds with vertex W on the right diagram and they are both listed first in the notation. You will be counted off for not following this rule.
Line of Refection
There are times when the line of reflection is not away from the figure but instead intersects the object as shown below.
See how moving the line of reflection affects the image by going to Explore! Line of Reflection.
Lines of Symmetry
Another concept of reflection is line symmetry. A figure has line symmetry if a line can be drawn through the figure where the figure maps on to itself perfectly when folded over the line.
Figures can have zero or multiple lines of symmetry as shown below.
Image 1 This figure has two lines of symmetry
Image 2 This figure has no lines of symmetry
Website
Math Open Reference: Reflection is a good interactive showing a line segment being reflected. Move a point to see how the corresponding point reacts to your move.
