What is a Rainbow? Understanding Colours in the Sky

Rainbows are one of the most beautiful and fascinating natural phenomena that appear in the sky. They appear as a colourful arc in the sky, typically after a rain. This phenomenon has captivated humans for centuries with its vibrant hues and mystical appearance. But what exactly is a rainbow, and how do those stunning colours form?

Let us dive into the science behind rainbows and uncover the magic that creates these spectacular displays.

The Science of Rainbows

A rainbow is an optical and meteorological phenomenon that occurs when light is refracted, dispersed, and reflected in water droplets. This process results in a spectrum of light appearing in the sky, forming a multicoloured arc. The main factors involved in the formation of a rainbow are sunlight and rain, which work together to create this dazzling effect.

Refraction and Dispersion

When sunlight enters a raindrop, it slows down and bends due to the change in medium from air to water. This bending of light is known as Refraction. Once inside the raindrop, the light is dispersed into its component colours because different wavelengths of light bend by different amounts. This dispersion of light separates the white sunlight into the colours of the spectrum.

Reflection

The light that is dispersed then gets reflected off the inside surface of the raindrop. This reflection causes the light to travel back through the raindrop and exit it bending again as it moves from water to air. This second refraction further separates the colours and directs them towards the observer’s eyes.

Colours of the Rainbow

The colours of a rainbow are arranged in a specific order, forming what is known as the visible spectrum. The main colours observed in a rainbow are red, orange, yellow, green, blue, indigo, and violet. This sequence can be remembered using the acronym VIBGYOR.

Visible Spectrum

1. Red

Red is the longest wavelength of visible light and appears on the outer most section of the rainbow. It is often associated with strong emotions like love and anger, making it a colour that grabs attention.

2. Orange

Orange is between red and yellow in the spectrum. It combines the energy of red with the happiness of yellow. Orange is often linked to creativity, enthusiasm, and warmth.

3. Yellow

Yellow is a bright and cheerful colour in the middle of the visible spectrum. It is often associated with sunshine, happiness, and positivity, which brings in a sense of joy and energy.

4. Green

Green is the colour of nature, symbolising growth, harmony, and freshness. It is a calming colour that promotes relaxation and is often seen as a sign of new beginnings.

5. Blue

Blue is a cool and serene colour that appears towards the inner part of the rainbow. This colour is often linked to tranquillity, trust, and stability, evoking calm and peace.

6. Indigo

Indigo is a deep blue colour that is sometimes hard to distinguish between blue and violet. It represents intuition, spirituality, and deep thinking, adding a touch of mystery to the rainbow.

7. Violet

Violet has the shortest wavelength and appears on the inner edge of the rainbow. This colour is often associated with creativity, luxury, and wisdom, bringing a sense of depth and imagination.

Types of Rainbows

Rainbows can come in various forms and sizes, each with its unique characteristics. Here are some common types of rainbows:

1. Primary Rainbow:
The most common type, formed by a single reflection inside the raindrop. The colours are brightest and appear in the order of VIBGYOR, with red on the outer edge and violet on the inner edge.
2. Secondary Rainbow: This rainbow forms outside the primary rainbow and is the result of two reflections inside the raindrop. The colours are reversed, with red on the inner edge and violet on the outer edge. Secondary rainbows are usually fainter than primary rainbows.
3. Supernumerary Rainbows: These are additional, faint rainbows that appear inside the primary rainbow. They result from the interference of light waves and appear as closely spaced, pastel-coloured bands.
4. Twinned Rainbow: Occasionally, a primary rainbow may split into two arcs, forming a twinned rainbow. This phenomenon occurs due to variations in the size of raindrops.
5. Fogbow: A fogbow is a rainbow that forms in fog rather than rain. It appears as a pale, white arc because the water droplets in fog are much smaller than raindrops, causing the colours to blend.

Interesting Facts About Rainbows

• Not the Same Rainbow: Each person sees a different rainbow because the angle at which light is refracted and reflected depends on the position of the observer’s eyes.
• Full Circle Rainbows: While we typically see rainbows as arcs, they can form full circles. This phenomenon is usually visible from an aeroplane or a high vantage point.
• Moonbows: Rainbows can also be created by moonlight, although they are much fainter and appear white because the moon’s light is not as bright as sunlight.
• Rainbows in Mythology: Rainbows have been a part of various mythologies and cultures. In Norse mythology, the rainbow bridge Bifröst connects the world of humans (Midgard) to the realm of the gods (Asgard).

Conclusion

Rainbows are a mesmerising display of nature’s beauty and a testament to the complex interplay of light and water. Understanding the science behind their formation allows us to appreciate their wonder even more. So, the next time you spot a rainbow in the sky, you will know the fascinating process that creates those brilliant colours.