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Splitting of White Light

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Last updated date: 22nd Jul 2024
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The Phenomenon of Splitting of White Light

Have you ever seen a beam of white light coming through your window then splitting and forming a rainbow on the ground? This phenomenon of splitting white light into its component colours is known as dispersion. 

White light consists of seven different colours. This means white light is a mixture of every other colour, i.e., violet, indigo, blue, green, yellow, orange, and red. Just like a rainbow where white light from the Sun comes out and falls on a raindrop following dispersion and split up into its seven component colours (VIBGYOR - VIOLET, INDIGO, BLUE, GREEN, YELLOW, ORANGE, AND RED, respectively)

Dispersion through a Window

Dispersion through a Window 

What is Dispersion?

The natural phenomenon by which white light is split into seven colours is known as Dispersion.

Why does Dispersion Happen? 

Dispersion of white light into its components is basically due to the change of speed of light of different wavelengths due to a change in density of objects or surroundings through which the light is passing through. 

How are different colours placed in different locations?

As there comes a change in the density of the medium through which light is passing the properties of the waves also change. Such as: 

  • Particles of the waves start covering a distance in a different time interval than it normally does.

  • The distance between two consecutive crests (highest displacement) and troughs (lowest displacement) also changes. 

The above causes changes in the wavelength of a particle in motion through a medium. With the change in wavelength comes variations in the bending of light. Every particular colour has a different wavelength due to a clear distinction of every colour. For example, red has the maximum wavelength and hence is less deviated, whereas violet has a minimum wavelength and hence is the most deviated. Due to which all different colours are dispersed and are made visible at different intervals as can be seen in the given image.

Deviation of Colours

Deviation of Colours

Refraction and Refractive Index 

As stated above, the splitting of white light into seven different colours happens due to a change in the density of the medium the light is passing through. This change in density of the medium causes light to bend, this phenomenon is called refraction and also causes a change in the speed of the light. That is why light travels faster in the rarer medium whereas travels slower in denser medium.

The ratio of the velocity of light in a vacuum with respect to the new velocity caused by the change in medium is called the refractive index of a medium. The phenomenon of refractive index is important while dealing with refraction. It tells us about how a particular kind of light is going to react in a particular medium while travelling and coming out of it. It also helps us to identify how the light is going to bend during its path.

Formula for Calculation of the Reflective Index of a Material

Formula for Calculation of the Reflective Index of a Material 

Experiment to see the Phenomenon of Dispersion at Home 

White light is basically the mixture of rainbow colours and when it splits, it forms a beautiful rainbow.

Warning: Adult supervision is necessary for any experiment for children. Do not look directly at the sun or into the reflection of the sun in a mirror.

Materials - water, sunlight

Tools - clean glass and a small or hand mirror


  • Fill the glass with water.

  • Put the mirror into the water such that it is at an angle 

  • Place the glass such that sunlight light falls directly onto the mirror. You may have to make shifts in the mirror's placement to find the correct angle.

Placement of Mirror Inside the Glass filled with Water

Placement of Mirror Inside the Glass filled with Water

  • Find a reflection on any wall. It will be easier to see if the room is dark.

  • Adjust the position of the mirror till you see a rainbow on the wall.

Splitting of White Light

Splitting of White Light


The phenomenon of splitting of white light is a very unique yet fascinating phenomenon occurring in nature. Through this phenomenon, one can identify the constituent visible colours composing a ray of white light. The most wonderful example of the same is the formation of a rainbow after rain which follows the principle of dispersion. Dispersion or the phenomenon of splitting of white light comprises various other phenomena that act simultaneously to perform this splitting, those phenomenons can be refraction, reflection, change in density of medium, relation of change in density in medium, speed of light, bending, relation of wavelength, and much more.

FAQs on Splitting of White Light

1. What is a prism?

A prism is a clear glass constituting triangular refracting surfaces which are used to disperse white light into constituting colours. Through a prism, if white light falls on one of the refracting surfaces it refracts, bends, and resolves into seven colours while merging out of the third surface and if a screen is placed in front of it, all the colours can be easily seen which are usually placed in accordance with their wavelength and deviation through refraction.

2. Is white the absence of light?

In Physics, a colour is a visible light with a specific wavelength. Black and white are not colours because they do not have specific wavelengths. Instead, white light contains all wavelengths of visible light. Black, on the other hand, is the absence of visible light.

3. Give some daily life examples of dispersion of light. 

Dispersion can be seen in the following places: 

  • Rainbow Formation - the refracting index of the air and that of water droplets are different due to which ray of white light refracting through the drop of water splits into seven colours. 

  • Reflection through a CD - white light falling on the shiny surface of the CD undergoes deviation and splits into various or seven colours. 

  • Refraction through a Prism or Diamond - diamond or prism has various refracting surfaces due to which white light bends and deviates and finally splits into different colours.

4. What causes the splitting of white light?

Prisms are specially shaped so that light passing through them bends. Some colours bend more than others as they pass through the prism, so they split apart. This means that a beam of white light going into a prism comes out as a spectrum of different colours.

5. Why does the white light split on the first refracting face of the prism?

Since different colours of light travel at different speeds, the refractive index is different for each colour. As a result, when white light passes through the refracting surface of the prism, its components bend into different angles, causing the single beam of light to separate.