It is a transformation which produces a mirror image of an object. The mirror image can be either about x-axis or y-axis. The object is rotated by180°.
Types of Reflection:
1. Reflection about x-axis: The object can be reflected about x-axis with the help of the following matrix
In this transformation value of x will remain same whereas the value of y will become negative. Following figures shows the reflection of the object axis. The object will lie another side of the x-axis.
2. Reflection about y-axis: The object can be reflected about y-axis with the help of following transformation matrix
Here the values of x will be reversed, whereas the value of y will remain the same. The object will lie another side of the y-axis.
The following figure shows the reflection about the y-axis
3. Reflection about an axis perpendicular to xy plane and passing through origin:
In this value of x and y both will be reversed. This is also called as half revolution about the origin.
4. Reflection about line y=x: The object may be reflected about line y = x with the help of following transformation matrix
First of all, the object is rotated at 45°. The direction of rotation is clockwise. After it reflection is done concerning x-axis. The last step is the rotation of y=x back to its original position that is counterclockwise at 45°.
Example: A triangle ABC is given. The coordinates of A, B, C are given as
A (3 4)
Find reflected position of triangle i.e., to the x-axis.
The a point coordinates after reflection
The b point coordinates after reflection
The coordinate of point c after reflection
a (3, 4) becomes a1 (3, -4)
Program to perform Mirror Reflection about a line: