A Prism is one of the most fundamental shapes in 3D geometry. Defined formally, it is a polyhedron with two congruent, parallel faces (called bases) and rectangular lateral faces connecting the corresponding sides of the two bases. The shape of the base gives the prism its name—if the base is a triangle, it is a triangular prism; if it is a hexagon, it is a hexagonal prism.
A History of Optics and Geometry
While prisms were studied by ancient Greek geometers like Euclid, their most famous moment in history occurred in the 1660s. During the Great Plague, a young Isaac Newton retreated to his family farm and began experimenting with glass triangular prisms.
[Image of Isaac Newton prism experiment light spectrum]At the time, people believed that color was a mixture of light and darkness. Newton darkened his room, made a tiny hole in the window shutter, and placed a prism in the beam of sunlight. The prism refracted the white light, spreading it out into a rainbow of colors (the spectrum). This proved that white light is actually a combination of all visible colors. This discovery laid the foundation for the field of Spectroscopy, which allows astronomers to determine the composition of distant stars today.
Anatomy of a Prism
To master the prism, one must understand its components:
- Bases: The two parallel ends. They define the prism's cross-section.
- Lateral Faces: The parallelograms (usually rectangles in a right prism) that connect the bases.
- Altitude (Height): The perpendicular distance between the two bases.
Formulas for Calculation
Prisms are consistent, which makes their formulas straightforward:
- Volume: Area of Base × Height
- Lateral Surface Area: Perimeter of Base × Height
- Total Surface Area: (2 × Area of Base) + Lateral Surface Area