Understanding Light Refraction with DIY Rainbow Experiments

3 October 2025

Have you ever wondered how a rainbow forms? Or why a straw looks bent when placed in a glass of water? These fascinating effects happen due to light refraction. Today, we're diving into this incredible phenomenon with some fun DIY rainbow experiments you can try at home!

What is Light Refraction?

Before we start experimenting, let's break it down. Refraction is what happens when light passes from one medium to another—like air to water—and changes speed. This causes the light to bend. Different materials bend light in different ways, and that's how prisms, magnifying glasses, and even rainbows work!

When sunlight hits a raindrop, it's refracted, or bent, as it enters the water. Then, it's reflected inside the droplet before exiting at a different angle. This bending and splitting of light reveal the beautiful spectrum of colors that make up a rainbow.

Now that we understand the basics, let’s create our own rainbows using simple household items!

DIY Rainbow Experiments

Here are a few easy, hands-on experiments to help you see refraction in action.

1. The Glass of Water Rainbow

One of the simplest ways to create a rainbow is using just a glass of water and sunlight.

What You'll Need:

- A clear glass or a transparent plastic cup
- Water
- A sheet of white paper
- A sunny window

Steps:

1. Fill the glass with water, about three-quarters full.
2. Place it near a sunny window so that sunlight shines through the water.
3. Hold the white paper on the other side of the glass.
4. Adjust the angle of the glass until you see a tiny rainbow appear on the paper!

What's Happening?

The water in the glass bends (refracts) sunlight, just like raindrops in the sky, breaking it into its component colors—red, orange, yellow, green, blue, indigo, and violet (ROYGBIV).

2. The Mirror and Water Rainbow

Want a larger and brighter rainbow? This experiment uses a mirror and a bowl of water to create a big, vivid spectrum.

What You'll Need:

- A small mirror
- A bowl
- Water
- A flashlight (if no sunlight is available)
- A white sheet of paper

Steps:

1. Fill the bowl with water.
2. Place the mirror inside the bowl at an angle, partially submerged.
3. If you're using sunlight, position the setup so that sunlight hits the submerged part of the mirror. If not, shine a flashlight onto the mirror.
4. Hold a white sheet of paper where the light is reflected.
5. A rainbow should appear on the paper! Experiment with angles to make the colors clearer.

What's Happening?

Light from the sun (or flashlight) bends as it enters and exits the water and mirror, splitting into different colors. This mimics what happens in raindrops when we see natural rainbows!

3. The Prism Rainbow

If you have a glass or plastic prism, you can create rainbows just like in a science lab! This is one of the best ways to see light dispersion in action.

What You'll Need:

- A glass or acrylic prism
- A light source (sunlight or a flashlight)
- A white sheet of paper

Steps:

1. Find a sunny spot or use a bright flashlight.
2. Hold the prism in the path of the light source.
3. Place a white sheet of paper to catch the refracted light.
4. Adjust the angle until a vibrant rainbow appears.

What's Happening?

A prism is specially shaped to bend and split light. Unlike a water droplet, which scatters light in all directions, a prism directs the colors into a clear, visible rainbow.

4. The CD or DVD Rainbow

No prism? No problem! An old CD or DVD can work just as well to create a mini rainbow.

What You'll Need:

- An old CD or DVD
- A flashlight
- A white sheet of paper

Steps:

1. Hold the CD near a bright light source.
2. Tilt it slightly until colors appear on the surface.
3. If you'd like, shine a flashlight onto the CD and reflect the light onto a white sheet of paper.
4. A rainbow will appear!

What's Happening?

CDs and DVDs have a reflective surface with tiny grooves that act like a prism, bending and separating the light into different colors.

The Science Behind Rainbow Colors

All of these experiments work because white light (like sunlight) is actually made up of different colors. These colors have different wavelengths—red has the longest wavelength, while violet has the shortest. When light bends during refraction, each wavelength bends at a slightly different angle, creating the beautiful spectrum we see as a rainbow.

Think of it like a crowded hallway at school—if a group of students rushes into a narrow door, the fastest ones get through first, while the slower ones take longer. Similarly, each light wave moves at a different speed when passing through glass, water, or air, separating into colors!

Everyday Examples of Light Refraction

Now that you know how refraction works, you'll start noticing it everywhere!

1. Bent Spoon in a Glass of Water

Ever seen a spoon look broken or bent in a glass? That's refraction at work—the light changes speed as it moves between air and water, making the spoon appear disjointed.

2. Glittering Rainbows in Soap Bubbles

Soap bubbles look shiny and colorful because of light refraction. The thin soap film bends light in different ways, creating swirling rainbow hues.

3. The Mirage on Hot Pavement

Ever noticed shimmering puddles on a hot road? That’s a mirage, caused by light bending when it passes through layers of hot and cool air.

Final Thoughts

Light refraction is truly a magical part of physics that we see in everyday life. From rainbows after a storm to the glow of a soap bubble, this phenomenon explains so many wonders of the world. And the best part? You don’t need fancy equipment to witness it—just a little curiosity and a few household items!

So, grab a prism, a glass of water, or even an old CD, and start creating your own rainbows today. Who knows? You might just see the world in a whole new light!