prism

Everyday

1. A solid shape with two ends that are the same flat shape and parallel, joined by flat sides (rectangles in a right prism). tree →
2. A block of glass or clear plastic, often a triangular one, that bends light and splits white light into a rainbow of colours. tree →

In the lessons

In maths geometry, prisms are named by their end shape: triangular prism, rectangular prism (a cuboid), hexagonal prism; pupils count faces, edges and vertices and find volume = area of the end × length. In science, a glass prism shows that white light is a mix of colours. Phrases: triangular prism, rectangular prism, through a prism.

Examples

• A triangular prism has 5 faces, 9 edges and 6 vertices. tree →
• A cereal box is a rectangular prism. tree →
• The prism split the sunlight into a rainbow. tree →
• Find the volume of the prism: the end area is 6 square cm and the length is 10 cm. tree →
• A Toblerone box is shaped like a triangular prism. tree →
• We shone a torch through the prism. tree →

Note

A cylinder has curved sides, so it is not usually called a prism; a pyramid comes to a point, so it is not a prism either. Volume of a prism = area of cross-section × length. Do not confuse with prison.