By Callum 
Have you ever stared in awe at a rainbow after a storm? Or noticed how a crystal in a window can paint a room with tiny, colorful lights? The object behind these beautiful displays is a simple yet powerful tool: the optical prism.
Prizmatem: A Word with Depth
In some languages, the idea of seeing the world through a prism is captured by the word prizmatem. This article is your guide to understanding the versatile prism. We will explore its geometric shape, the science of how it manipulates light, and the incredible technologies it makes possible in our everyday world.
What is a Prism? A Geometric Foundation
Before we see how a prism creates a rainbow, we need to know what it is. In geometry, a prism is a type of three-dimensional solid called a polyhedron, which means all its faces are flat and well-defined.
A prism has two identical ends that are parallel to each other. These are called the bases. The faces that connect the bases are always parallelograms. Because a prism must have flat faces, a cylinder, which has a curved surface, is not classified as a prism.
A Family of Shapes
Prisms get their names from the shape of their bases. Since the base can be any polygon, there is a whole family of prism shapes. Many of these are common objects you see every day in your home, school, or workplace.
Common Prism Types You See Every Day
| Prism Type | Base Shape | Real-World Example |
| Triangular Prism | Triangle | A camping tent or the classic glass prism from science class. |
| Rectangular Prism | Rectangle | A shoebox, a brick, or a standard fish aquarium. Also known as a cuboid. |
| Square Prism | Square | A pair of dice. If all faces are perfect squares, it is a cube. |
| Pentagonal Prism | Pentagon | Sections of the Pentagon building in the United States. |
| Hexagonal Prism | Hexagon | A new, unsharpened pencil or the cells in a honeycomb. |
Standing Straight or Leaning? Right vs. Oblique Prisms
Prisms are also classified by their orientation in space. A right prism stands up straight, with its side faces being rectangles that are perpendicular to the base surface.
An oblique prism looks like it is tilted, because its joining edges are not at a right angle to the bases. Its side faces are parallelograms instead of rectangles, giving it a slanted appearance.
How a Prizmatem Creates a Rainbow
The Secret is in the Angles
The most exciting part of a prism’s story is how it creates a rainbow. The magic of a prizmatem happens because of a key geometric feature. In a triangular prism, the two faces that light passes through are flat but not parallel to each other. This simple fact is the secret to unlocking the colors hidden in white light through the process of dispersion.
Bending Light: The Magic of Refraction
The process starts with refraction. When light moves from one material to another, like from air into glass, it changes speed and bends. Imagine a lawnmower driving from a sidewalk onto grass at an angle. The first wheel that hits the grass slows down, causing the whole mower to turn. Light acts in a similar way when it enters a prism, bending at a different angle.
White Light’s Hidden Colors
What we see as white light is actually a mix of all the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet (ROYGBIV). Each of these colors travels as a wave with a slightly different wavelength and frequency.
Why Different Colors Bend Differently: Understanding Dispersion
When light enters the prism’s glass, each color slows down by a different amount. Violet light, with the highest frequency, slows down the most. Red light, with the lowest frequency, slows down the least. This happens because the atoms in the glass interact with the light waves. They “hold on” to the higher-energy violet light for a fraction of a second longer than they do the lower-energy red light, causing it to travel more slowly through the glass.
This differential bending is called dispersion. It’s what starts to separate the colors inside the prism, revealing the full visible spectrum in brilliant detail.
The Second Bend: Fanning Out the Spectrum
When the light reaches the other side of the prism, it bends again as it exits back into the air. This second bend increases the separation between the colors, fanning them out into the full spectrum we see as a rainbow across the surface.
Why a Rectangle Doesn’t Make a Rainbow
If you shine light through a rectangular block of glass, the colors separate a little bit when they enter. However, because the exit face is parallel to the entry face, the second bend reverses the first. The colors recombine and emerge as white light again, canceling out the rainbow effect.
A World of Wonders: Prisms All Around Us
Creating rainbows is a prism’s most famous trick, but these objects are essential in countless devices we use every day.
Seeing Clearly: Prisms in Optical Instruments
When you use binoculars, you’re looking through a set of Porro prisms. These prisms use total internal reflection to flip the image right-side up, so what you see isn’t inverted or distorted. Similarly, the bump on top of an SLR camera holds a pentaprism, which directs the light from the lens to the viewfinder so you can see exactly what the camera sees in real time.
A Medical Marvel: Correcting Vision with Prisms
For people with double vision (diplopia), prisms are a life-changing tool. Special prism lenses in eyeglasses bend light to realign the images from each eye, allowing the brain to see a single, clear picture. Eye doctors also use prisms to diagnose and measure eye alignment issues with precision and accuracy.
Unlocking the Universe: Prisms in Science and Technology
Scientists use prisms in spectrometers to analyze light from distant stars. By splitting the starlight into a spectrum, they can identify the chemical “fingerprints” of elements and determine what stars are made of. Prisms are also critical in laser systems and telecommunications, where they are used to steer and split beams of light with incredible precision and reliability.
Building the Future: Prisms in Architecture and Art
The strong, simple shape of the prism is also used in architecture. Some buildings use triangular prism shapes for roofs to help shed heavy snow and rain. Creative photographers also use prisms, holding them in front of their camera lens to create artistic rainbow flares and abstract light effects in their photos and videos.
Explore with Your Own Prizmatem
The best way to appreciate a prism is to see it in action. You can do simple experiments at home to see these effects for yourself and better understand how prisms work.
The Water Prism Experiment
Fill a clear, straight-sided glass with water and place it on a sunny windowsill. Put a white sheet of paper on the floor. With a little adjustment, the glass of water will act as a prism and cast a faint rainbow onto the paper, just like magic.
The CD Rainbow
Hold the shiny side of a CD or DVD up to a light source and tilt it. You will see vibrant rainbows dance across its surface. The tiny tracks on the disc separate the light into its component colors, demonstrating diffraction and dispersion.
Finding Prisms in Plain Sight
Keep an eye out for prisms in your daily life. The beveled edges of a mirror or a piece of decorative glass can often throw small splashes of color onto walls when the light hits them just right.
The End of the Rainbow
Our journey has shown us that a prizmatem is much more than a simple block of glass. Its elegant geometric shape holds the power to unlock the hidden spectrum of colors in light. This simple principle is the foundation of tools that help us see across vast distances, correct our vision, and understand the universe. The next time you see a rainbow, you’ll know the beautiful science behind the magic of prisms.