Rainbow: Formation, Types, Colours, and Simple Experiments

Rainbows happen to be the most magnificent phenomena found in nature. As opposed to the Sun, which radiates light, or the Moon that shines, the rainbow cannot be touched or approached. The rainbow is a light show occurring in nature, resulting from sunlight interacting with small drops of water in the atmosphere. Incredible, isn’t it? Have you ever been curious about the process by which a rainbow forms? Scientists have analysed this phenomenon for hundreds of years and finally managed to establish that it was due to sunlight being reflected, refracted, and diffracted in drops of water. This article seeks to give an insight into what a rainbow is and how it forms, as well as its various types and easy-to-do experiments with rainbows.

Table of Contents

• What Exactly Is a Rainbow
• The Science Behind Rainbow Formation
• Why Rainbows Appear as Curved Arcs
• Easy Rainbow Experiments You Can Do at Home
• Interesting Info About Rainbows

What Exactly Is a Rainbow

A rainbow is one of the most stunning natural phenomena we can witness. It appears as a colourful arc in the sky, formed when sunlight interacts with tiny water droplets in the atmosphere. But how exactly does this happen? Let’s discuss. When sunlight enters a raindrop, it bends, reflects inside, and then exits, splitting into its component colours. This bending and splitting of light, known as refraction and dispersion, creates the beautiful arc we see in the sky.

Now you might be curious: why do rainbows always show the same order of colours ?

The answer goes back to the work of Sir Isaac Newton in the 17th century. Newton discovered that white light is made of many colours, and when it passes through a prism, it separates into red, orange, yellow, green, blue, indigo, and violet.  And here’s a fun fact: if all the colours of a rainbow were combined, they would produce white light again.

To help remember the order of the rainbow colours, the acronym VIBGYOR (or ROY G. BIV) is often used, which stands for Violet, Indigo, Blue, Green, Yellow, Orange, and Red. To understand the colours better, here’s a table showing each rainbow colour with its approximate wavelength:

Colour	Wavelength (nm)	Features	Meaning of each Colour
Red	620 to 750	The first colour of the rainbow is made by mixing blue and red.	Energy, vitality, wisdom
Orange	590 to 620	The second colour is formed by mixing blue and violet.	Creativity, joy
Yellow	570 to 590	The third colour is seen when light scatters through water droplets or tiny particles.	Sunlight, optimism, intellect
Green	495 to 570	The fourth colour is made by combining blue and yellow.	Healing, nature, balance
Blue	450 to 495	The fifth colour is formed by mixing red and green.	Calmness, spirituality, trust
Indigo	425 to 450	The sixth colour is a mix of red and yellow.	Intuition, deep knowledge
Violet	380 to 425	The seventh and final colour of the rainbow is a primary colour that appears at the end.	Imagination, spirituality

In simple words, Rainbows are more than just colourful arcs in the sky; they show how sunlight and water work together to create a beautiful natural phenomenon that anyone can observe and enjoy. Now let’s look at the science behind this and break it down.

The Science Behind Rainbow Formation

Even though the colour of sunlight looks white, it is actually made up of many colours. Under the right conditions, these colours separate and form the beautiful arcs called rainbows that we see in the sky. So, how does the rainbow form? Let’s break it down step by step so that it will be easier to understand. 

You can think of it like this: sunlight enters a drop → bends → reflects → splits into colours → bends again → and then comes out to join millions of other drops → creating the rainbow we can see.

• First, when sunlight enters a raindrop, it slows down and bends. This bending of light is called refraction. 
• Inside the droplet, the light hits the back surface and reflects (reflection of light). As it reflects, the white light starts to split into its different colours. This splitting is called dispersion.
• After reflecting, the light leaves the droplet and bends once more. Because each colour bends at a slightly different angle, the light spreads out into a smooth, colourful arc. 

When millions of raindrops do this at the same time, the combined effect creates the rainbow we admire in the sky.

Why Do Rainbows Appear as Curved Arcs

Have you ever noticed that rainbows always appear opposite the Sun? It’s not a coincidence. Sunlight enters raindrops, bends, reflects inside, and splits into all the different colours we see. This happens at a particular angle, usually around 42 degrees, which actually forms a full circle.

But from the ground, we rarely see the full circle because the Earth blocks the bottom part. That’s why most of the time, rainbows appear as the familiar curved arc. If you happen to be on a plane or standing on a high mountain, you might even catch a glimpse of a complete circular rainbow.

So, now we understand why rainbows form their familiar arcs in the sky, but did you know that not all rainbows look the same? Let’s take a closer look to understand the reason:

1. Primary Rainbow: This is the brighter and more common rainbow. The red colour appears on the outer edge, while violet is on the inside. It is created by one internal reflection of light inside the raindrops.
2. Secondary Rainbow, a fainter rainbow that appears outside the primary one. Its colours are reversed, with red on the inside and violet on the outside. This happens due to two internal reflections inside the droplets.
3. Moonbows, these rainbows are formed by moonlight instead of sunlight. They are usually faint and appear whitish because the light is much weaker.
4. Fogbows formed from tiny fog droplets, fogbows are almost white and have very faint colours.
5. Higher-Order Rainbows: These are rare rainbows caused by three or more internal reflections inside raindrops. They are difficult to see but do occur under the right conditions.

Interestingly, rainbows could also form on Titan, Saturn’s largest moon, because of methane rain. These would be visible only in infrared light. Even with all these types, one thing remains amazing: each rainbow shows how sunlight and water can create stunning displays in nature. The fact!! No two people see exactly the same rainbow. Its shape and position depend on where you stand in relation to the Sun and the raindrops. Sometimes, under the right conditions, a double rainbow can appear, with the secondary arc showing the colours in reverse order. 

Easy Rainbow Experiments You Can Do at Home

A rainbow may look magical in the sky, but you don’t always need rain to see one. With a few simple materials, you can create rainbow effects right at home and understand the science behind them. Here are two simple experiments:

1. 1. A rainbow with a Prism is a simple glass object, but it can unlock the hidden colours inside sunlight. When you place a prism in direct sunlight, the light bends as it passes through. By rotating the prism carefully, you’ll notice a band of colours projected onto a white surface. This happens because of refraction and dispersion; the light slows down inside the prism, bends, and separates into its seven colours. It’s the same process nature uses with raindrops to form rainbow colours in the sky.

2. Now let’s try something different, creating a rainbow in a jar. All you need is sugar, water, food colouring, spoons, and a few glasses. 

• First, prepare coloured sugar water solutions with different amounts of sugar. The more sugar you add, the denser the liquid becomes.
• Next, carefully layer these solutions in a single jar, starting with the densest at the bottom and the lightest on top. 
• If done slowly, you’ll see bands of colour stacked neatly, looking like a rainbow in liquid form.

This experiment shows how density affects the way liquids settle. Just like the prism reveals light’s hidden colours, this activity reveals how science can create rainbow-like layers in everyday life.

Interesting Facts About Rainbows

Rainbows can appear not only after rain but also from mist, water sprays, or waterfalls. Every observer sees a rainbow differently because it depends on the viewing angle. A rainbow is not a physical object, so it is impossible to reach its end. Seeing two rainbows at the same time, called a double rainbow, is rare but possible.

In this article, we learned about rainbows, including how they form, why their colours always appear in the same order, the different types that appear in the sky, and simple experiments you can try at home. This shows that rainbows are not only beautiful sights but also clear examples of how sunlight, water, and physics work together to create something remarkable.