Why do we see only seven colours in a rainbow?

In one line

The rule

White light splits into seven visible colors when it passes through water drops, due to refraction (bending), reflection (bouncing), and dispersion (spreading out) of light.

Let's understand it simply

Imagine sunlight as a big box of crayons, all mixed together. When sunlight passes through raindrops, the drops act like tiny glass prisms. They break up the white light into its different colors, just like a prism does in your classroom. Our eyes can see these colors as red, orange, yellow, green, blue, indigo, and violet. These are the main colors we notice, even though there are actually many more shades in between.

How it works

1. Sunlight hits a raindrop in the sky.
2. The light bends (refracts) as it enters the drop.
3. Inside, the light bounces (reflects) off the back of the drop.
4. The light bends again as it leaves the drop.
5. Each color bends by a different amount, so they spread out into a band.
6. Our eyes see these as seven main colors.

The story behind it

Isaac Newton, a famous scientist in the 1600s, used a glass prism to split sunlight into colors. He noticed many colors but named seven main ones, linking them to musical notes and days of the week. This is why we learn about seven colors in a rainbow, even though the real rainbow has many more shades.

Where you see it in real life

• After rain, when the sun comes out → Sunlight passes through raindrops → You see a rainbow in the sky.
• Spraying water from a pipe in sunlight → Water drops act like tiny prisms → A small rainbow appears.
• Looking through a glass prism in school → White light splits into seven colors → Same effect as a rainbow.
• CD or DVD surface in sunlight → Tiny lines act like prisms → You see rainbow colors.

Why it matters

• Helps us understand how light works and how we see colors.
• Used in making colorful lights and decorations (like Diwali lights).
• Important in science to study light and optics (how light behaves).
• Helps in weather prediction and understanding rain patterns.

Common mistakes

• Thinking there are only seven colors in a rainbow: Actually, there are many more, but we name seven main ones.
• Believing the colors are always the same brightness: Sometimes, some colors are faint or hard to see, depending on the weather and your eyes.
• Mixing up the order: The order is always red, orange, yellow, green, blue, indigo, violet (from outside to inside).

Remember it

Remember "VIBGYOR"—the first letters of Violet, Indigo, Blue, Green, Yellow, Orange, Red. These are the seven colors you see in a rainbow.