Science Behind Rainbow Formation


Rainbow is one of the most splendid masterpieces of nature. When the rain and the sunlight combine in a very specific way, rainbows happen. It is a natural spectrum of light in the form of bows appearing in the sky when the sunlight falls on the droplets of rain. Rainbow is an excellent result of dispersion, refraction, and reflection of light from rain droplets, in the atmosphere.

science behind rainbow

The formation of the primary rainbow is a result the following three-step process which is mentioned below.

Dispersion of Light

Visible light or white light consists of a collection of component colors. These colors can be observed when white light passes through a prism. When the light passes through a prism the visible light is separated into its component colors i.e. red, orange, yellow, green, blue and violet. This property of separation of white light into its different colors is called as Dispersion of Light.

Reflection of Light

Reflection is a common word which is frequently used in the field of mathematics and physics. Reflection occurs when light bounces off an object. When a ray of light approaches a smooth and polished surface, the light ray bounces back, this is called as a reflection of light. It is one of the most important phenomena for the formation of rainbow.

Refraction of Light

The bending of light when it travels through different media is called as refraction. Refraction also happens with sound water and other waves. The bending of light by refraction makes it possible to have magnifying glasses, lenses, rainbow, etc. even eyes depend on refraction of light. Without this property, we will not be able to focus the light on our retina.

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Due to this, each droplet of rainwater acts as a tiny prism that disperses the sunlight and reflects it back to our eyes. As a result, when we look at the sky, the net effects of the vast array of raindrops forms a circular arc of VIBGYOR (red, orange, yellow, green, blue, indigo and violet).

The Path of Light Through a Raindrop

There are numerous paths by which the sunlight can pass through a raindrop. Each path of the light is characterized by bending away and towards from the normal.

The rainbow is always formed in the direction opposite to the sun. To see a rainbow, one must have the sun behind him/her and the water droplets in front. When light enters the spherical rain droplets, it is refracted and dispersed. Due to this different colors of the light end at different angles. When the sunlight falls on the back of the water drops, total internal reflection takes place. Then the raindrops again refract the different colors of light, when it comes out of it. Thus a magnificent rainbow is formed in the sky.

Rainbows are not limited to the dispersion of sunlight by rain droplets. There are other examples of formation of a rainbow, like, due to the splashing of water at the base of a waterfall. Join BYJU’S and learn various interesting science facts and science experiments and enjoy science and maths in a better way. Visit Science Discussions and join the online education discussion forum to get involved in the open discussion on various interesting science topics. Subscribe to BYJU’S YouTube Channel to watch interactive videos on various science topics.


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