CLASS-7
GEOMETRY - SYMEETRY - REFLECTION

REFLECTION -

Reflection (Mirror) Symmetry occurs when a shape or object can be divided by a line so that each half is a mirror image of the other. The dividing line is called the line of symmetry or axis of symmetry.

Key Features of Reflection Symmetry:-

  • Line of Symmetry:- A line along which the shape can be folded so that the two halves match perfectly.
  • Mirrored Halves:- One side is the exact mirror of the other side.
  • The reflected parts have identical size and shape but opposite orientation (left becomes right, and vice versa).

Examples of Reflection Symmetry:-

  1. Geometric Shapes:-   Square:- 4 lines of symmetry (vertical, horizontal, and two diagonals).  Rectangle:- 2 lines of symmetry (vertical and horizontal). Circle:- Infinite lines of symmetry.  Equilateral Triangle:- 3 lines of symmetry (each passing through a vertex and the midpoint of the opposite side).
  2. Letters:- Letters like A, M, T have vertical symmetry. Letters like B, C, D, E have horizontal symmetry.
  3. Nature:-    Butterflies:- Their wings exhibit bilateral symmetry along a vertical axis.  Human faces and bodies:- While not perfectly symmetric, they are often approximated as having vertical symmetry.
  4. Architecture and Art:- Buildings such as the Taj Mahal and cathedrals use reflection symmetry for visual balance. Kaleidoscopic patterns also rely on reflection symmetry to create visually appealing designs.

Types of Reflection Symmetry:-

  1. Vertical Symmetry:- The line of symmetry runs up and down (along the y-axis). Example:- The letter "A".
  2. Horizontal Symmetry:- The line of symmetry runs left to right (along the x-axis). Example:- The letter "B".
  3. Diagonal Symmetry:- The line of symmetry is slanted, forming an angle with the axes. Example:- A square has two diagonal lines of symmetry.

Real-Life Applications:-

  • Road Signs:- Many traffic signs use reflection symmetry to make them easy to recognize from different angles.
  • Logos:- Companies use symmetrical logos to create a sense of harmony and balance (e.g., Toyota).
  • Art and Design:- Reflection symmetry is used in patterns, wallpapers, and architecture to enhance aesthetics.