Symmetry Summary GLY 4200 Lab 5 - Fall, 2017
Definitions Motif: the fundamental part of a symmetric design that, when repeated, creates the whole pattern Operation: some act that reproduces the motif to create the pattern Element: an operation located at a particular point in space
2-D Symmetrical Pattern
Symmetrical Pattern A pattern consisting of two motifs
Symmetrical Pattern is the symbol for a two-fold rotation, known as a diad
180 Degree Rotation Rotate in two steps
Three Fold Rotation 360o/3 = 120o rotation to reproduce a motif in a symmetrical pattern is the symbol for a three-fold rotation, known as a triad
N-Fold Rotations Respectively, 360o, 180o, 120o, 90o, and 60o
Reflection Reflection across a “mirror plane” reproduces a motif is the symbol for a mirror plane
Inversion Inversion through a center to reproduce a motif in a symmetrical pattern = symbol for an inversion center
Lab Exercise For lab, examine each object Report all symmetry For rotation, the fold and number of each type of rotational axis present Example: 1A4, 2A2 For reflection, total number of mirror planes present, if any For inversion, yes or no (does it have a center or doesn’t it?)
Results Keep a copy of your results for next week’s lab – you need to turn in one, and have one copy for lab 6