A reflection is a transformation that produces a mirror Image of an object. The mirror image for a 2-D reflection is generated relative to an axis of reflection by rotating the object 1800 about the reflection axis we can choose an axis of reflection in the xy plane or perpendicular to x-y plane.
• When the reflection axis is a line in the xy plane, the rotation path about this axis is in a plane perpendicular to xy plane.
• For reflection axis that is perpendicular to xy plane, the rotation is in xy plane.
(i) Reflection about the line y =o, the x-axis is accomplished with transformation matrix :

This transformation keeps x-values the same but flips the y-values of coordinate positions.
(ii) Reflection about the y-axis flips x-coordinates keeping y-coordinates the same The matrix for this transformation is :

Now elements of the reflection matrix can be set to values other then ±1 values whose magnitudes are greater than 1 shift the mirror Image farther from the reflection axis & values with magnitude less than 1 brings the mirror image closer to the reflection axis.