What Causes the Appearance of Rainbows in Bubbles?

Has anyone ever informed you that every cloud has a positive aspect? Some days this statement may appear to be true, while other days may seem gloomy. However, when those clouds bring rain, you might gaze up at the sky and witness something extraordinary. What are we referring to? A rainbow, obviously!

Following a heavy rainstorm, the Sun occasionally manages to break through the clouds. As you step outside into the humid air, inhaling the fresh fragrance that often follows a storm, you may search the horizon for those magnificent colors – red, orange, yellow, green, blue, indigo, and violet – that we refer to as a rainbow.

Rainbows seem to be a reward for enduring those rainy days. But did you know that you can sometimes observe rainbows on a bright, dry, sunny day as well? If you have ever blown bubbles in the backyard on a warm summer day, then you are aware that those small orbs that hover around your head sometimes shimmer with the colors of the rainbow. Why does this occur?

To comprehend why you often see the colors of the rainbow in bubbles, we must examine those bubbles more closely. What are those bubbles made of anyway? If you guessed soap, then you are on the right track!

Bubbles resemble tiny transparent balloons filled with air, but they are not made of latex like most balloons. Instead, bubbles consist of extremely thin layers of soap and water. How thin are they? The walls of a soap bubble are only millionths of an inch thick!

A bubble’s walls are similar to a sandwich. There is an ultra-thin layer of soap on the outside and on the inside. These soap layers enclose an ultra-thin layer of water in the middle. When you blow on soapy water, the ultra-thin soap and water film traps air and keeps it inside due to surface tension. Bubbles form spheres because that is the smallest stable structure they can adopt.

As loyal Wonder Friends already know, rainbows appear in the sky after it rains because raindrops high up in the atmosphere refract or bend sunlight like countless tiny prisms. Sunlight is considered “white” light, or a combination of all the visible light wavelengths. However, when raindrops act as prisms and refract or bend sunlight, we can then perceive the different wavelengths (and hence colors) present in sunlight.

We see colors in bubbles for a different reason. When light waves strike bubbles, some of the light is reflected back to your eyes from the outer surface of the bubble. Additionally, some of the light is reflected back to your eyes from the inner surface, which is slightly further away by a few millionths of an inch.

These two sets of waves that return to your eyes interfere with each other. Some waves combine, intensifying certain colors. Other waves cancel each other out, eliminating specific colors. The remaining colors that reach your eyes are the ones you see, known as interference colors.

Bubbles display various colors due to the different thicknesses of the soap and water layers that form their walls. Each color corresponds to a specific thickness, causing the bubbles to appear to change colors as they move. By contracting and expanding, the walls of the bubbles change thickness and result in different interference colors.

To further explore this phenomenon, here are some activities you can try with a friend or family member:

1. Get a bottle of bubbles and head to the backyard. Blow bubbles until you see rainbows! If you don’t have bubbles at home, visit a local store to get a bottle that comes with a wand.

2. Create your own bubble solution using homemade recipes. Check out “How To Make Bubbles for Kids” online for seven different recipes. Don’t forget to gather any additional ingredients you may need from the store. Enjoy the process of making and using your homemade bubble solution!

3. Imagine what people might have thought about bubbles and rainbows centuries ago. Come up with your own non-scientific explanation for why rainbows appear in bubbles. Was it the work of trapped spirits or a miniature world with eternal rain? Use your imagination to craft a creative story to share with your friends and family.


1. What causes a rainbow to appear in bubbles?

A rainbow appears in bubbles due to the phenomenon of light refraction and reflection. When light passes through the thin film of soap solution that forms the bubble, it undergoes refraction, bending as it enters and exits the film. This bending of light causes the different colors of light to separate, creating a spectrum of colors that we see as a rainbow.

2. Why do bubbles create circular rainbows?

Bubbles create circular rainbows because the soap film that forms the bubble is round in shape. When light enters the film, it undergoes multiple reflections and refractions within the film. These reflections and refractions cause the light to travel in a circular path, resulting in a circular rainbow.

3. Can you see a rainbow in all bubbles?

No, a rainbow can only be seen in bubbles that have a thin film of soap solution. Bubbles formed with just water or other liquids do not create the required thin film for light refraction and reflection. The soap film is essential for the formation of a rainbow in bubbles.

4. Why do the colors in a bubble rainbow appear so vibrant?

The colors in a bubble rainbow appear vibrant due to the interference of light waves. As light enters the soap film, it reflects off the inner and outer surfaces of the film. This reflection causes the light waves to interfere with each other, amplifying the intensity of certain colors. The amplified colors appear more vibrant to our eyes.

5. Can you create a rainbow in bubbles without sunlight?

Yes, it is possible to create a rainbow in bubbles without sunlight. Artificial light sources, such as a flashlight or a colored LED light, can also create the necessary light for the refraction and reflection to occur in the soap film. However, sunlight is the most common and natural light source for observing rainbow bubbles.

6. How can you make the rainbow in bubbles last longer?

To make the rainbow in bubbles last longer, you can try adding glycerin to the soap solution. Glycerin helps to increase the viscosity of the solution, making the soap film thicker and more resistant to bursting. A thicker film allows for more prolonged refraction and reflection of light, prolonging the appearance of the rainbow in the bubbles.

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