It can be observed that if the angle of rotation of a figure is a factor of \(360\)\(º\), then it will have a rotational symmetry of order more than \(1\).
It can be checked that \(45º\) is a factor of \(360º\) but \(17º\) is not.
Therefore, the figure having its angle of rotation as \(45º\) will have its rotational symmetry of order more than \(1\).
However, the figure having its angle of rotation as \(17º\) will not be having its rotational symmetry of order more than \(1\).
Shape | Centre of Rotation | Order of Rotation | Angle of Rotation |
---|---|---|---|
Square | |||
Rectangle | |||
Rhombus | |||
Equilateral Triangle | |||
Regular Hexagon | |||
Circle | |||
Semi-circle |
Match the items given in Column I with one or more items of Column II.
Column I | Column II |
(a) A plane mirror | (i) Used as a magnifying glass. |
(b) A convex mirror | (ii) Can form image of objects spread over a large area. |
(c) A convex lens | (iii) Used by dentists to see enlarged image of teeth. |
(d) A concave mirror | (iv) The image is always inverted and magnified. |
(e) A concave lens | (v) The image is erect and of the same size as the object. |
- | (vi) The image is erect and smaller in size than the object. |