Dispersion of Light through a Prism

Last Updated : 04 Feb, 2024

Dispersion of Light happens when white light is split into its constituent hues due to refraction. Dispersion of Light can be achieved through various means but the most common way to achieve dispersion of light is through Prism. Dispersion of light by a prism results in the breaking of white light into its seven constituents.

Dispersion of Light through a prism is achieved by allowing the white light to fall on the prism and passing the light through the prism to break it into its constituent colours. In this article, we will learn about the Dispersion of Light, its experiment and others in detail.

What is Dispersion of Light?

Dispersion is defined as the spitting of white light into different colors when passed through a prism.Â

The white light after passing through the prism splits into seven different colours namely,Â

• Violet
• Indigo
• Blue
• Green
• Yellow
• Orange
• Red

Together these colours are written as VIBGYOR.

Dispersion Of Light Through Prism

When light passes from one medium to another medium speed of propagation of light changes as a result the light is refracted. Now when the light passes through the prism, it gets refracted this refraction of light makes the light split into various colours and this phenomenon is called the dispersion of light through the prism.

Different colours in the light range have different wavelengths. Therefore, the speed at which they bend varies depending on the wavelength, in which the Violet light bends most, and the Red bends the least. As a result, white light coming out from the prism breaks into the spectrum of the light.

Diagram of Dispersion of Light Through Prism

The image below shows the dispersion of light through a prism and the formation of a spectrum by white light.

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Angle of Deviation

The measure of refraction in the path of light after passing through the prism is measured by measuring the angle of deviation. The angle of deviation is defined as the angle made between the incident ray of light entering the prism and the refracted ray emerging out of the prism.

The deviation of the light waves after passing through the prism is inversely proportional to the wavelength of the light as the wavelength of the Violet light is the least and so the violet light get deviates the most, whereas the wavelength of the red light is the most and hence it gets deviates the least.

The image below shows the angle of deviation:

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The visible pattern of the spectrum observed by us when the light passes through the prism is because of the change in the wavelength of the various colour lights.

Visible Light Spectrum

The light disperses into a wide range of colours after passing through a glass prism. We can see this by looking at it from a different perspective. The refractive index associative with a material is not fixed it varies with the frequency of the light used.

• If white light passes a glass prism it gets refracted twice, first when the light strikes the prism the light ray gets deviated from the air to the glass surface and its speed decreases whereas when the light ray leaves the glass prism it again gets deviated from the glass to the air surface and its speed is increased.
• Inside the glass prism, the speed of the light rays remains constant.
• The surface of the prism is not parallel and hence the light ray does not follow the same path and gets deviated.

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This deviation in the white lights makes the spectrum of the light visible and we observe the visible spectrum of the light. For example, the spectrum observed on the oil drop is the visible spectrum of the light.

Prism Experiment

The first experiment of light passing through the prism was first conducted by the great scientist Newton. He allows white light to pass through a prism hoping to get white light to the other end. But to his surprise, he found that white light gets changed to the spectrum of the seven colours. He named this phenomenon as dispersion of light.

Through this experiment, he concluded that light is made up of a spectrum of light. To further prove his experiment he from some other tests as

• He allows the light of only one wavelength to pass through the prism and observes the light ray coming out of the prism and found that this ray only gets refracted and so no sign of dispersion.
• He realized that only white light shows dispersion, as it is made of several colours of light and all these colours of light, have different wavelengths thus their refraction is not the same they all get deviate differently passing through the prism and allowing to form the spectrum of light.Â
• He concludes that violet light has the shortest wavelength and hence it deviates most whereas red light has the highest wavelength and hence it deviates the least.

Examples of Dispersion of Light

Various examples where the dispersion of light is observed are,

Formation of RainbowÂ

Dispersion of light is the reason behind the formation of the rainbow. When it rains the tiny water droplets remain in the air. When the sunlight passes through water droplets the light gets dispersed and we see the dispersed light in the form of a Rainbow.

Spectrum observed on Oil Droplets in Water

When oil droplets fall on water, we see the different colours in them. This is because the light undergoes refraction when it passes from the oil to the water medium or vice versa. Hence the light is dispersed and we see the spectrum of different colours in the oil droplets.

FAQs on Dispersion of Light

Q1: What is Dispersion of Light?

When white light passes through a glass prism, it separates into its spectrum of colours (in order violet, indigo, blue, green, yellow, orange, and red), this process is known as Dispersion.

Q2: What is Prism?

A prism is glass apparatus made of transparent glass. It has three rectangular lateral surfaces and two triangular faces that are inclined at an angle. It dispersed the white light passing through it.

Q3:What is Refraction of Light?

When the light ray changes its medium of propagation its deviates from its path this phenomenon is called the refraction of the light.

Q4: What is the Difference between Reflection and Refraction of Light?

Refraction of light is the change in the direction of light when it changes its propagation of the medium whereas reflection is the change in direction of the light after striking through a solid surface.

Q5: What are Examples of Refraction of Light?

Various examples of the refraction of light are,

• Twinkling of Stars
• Formation of Rainbow
• Red light of the sky during sunrise and sunset

Q6: What is VIBGYOR Full Form?

When the light ray is passed through the glass prism it gets deviated into the spectrum of the light in the order VIBGYOR and the full form of the VIBGYOR is,

• Violet
• Indigo
• Blue
• Green
• Yellow
• Orange
• Red

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