Dispersion by a prism

Dispersion of light occurs when the light enters a glass prism and divides into a spectrum of colours (in sequence-violet, indigo, blue, green, yellow, orange, and red).

Let’s discuss the dispersion of light by a prism to clearly understand the dispersion of light through a prism.

When light travels through different mediums at different speeds, it bends or refracts, causing it to bend or refract. When it passes through a prism, it gets refracted towards the base of the triangle. 

Many hues in the light spectrum have different wavelengths. As a result, the rate at which they bend varies by wavelength, with violet bending the most and red bending the least due to its longest wavelength. 

When white light is refracted via a prism, it disperses into its spectrum of colours, and that’s what is called dispersion of light by a prism. 

Prism Experiment

The first person to experiment with light passing through a prism was Newton. After passing sunlight through the prism, he expected to see the white light on the other side of the screen, but instead saw a spectrum of light after dispersion. He had an intuition about the significance of this location, but he opted to do something else to confirm it.

He permitted only one colour (and thus one wavelength of light) to flow through the prism by limiting the size of the intake. The ray of light was refracted and did not disperse any farther.

As a result, in his dispersion of light by a prism experiment, he learned that different wavelengths of light cause different colours of the spectrum to bend differently. Because of their shorter and longer wavelengths, he discovered that violet bent the most and red bent the least.

What causes the Dispersion by a prism?

We all have been studying refraction through a prism since class 10, and we have a brief idea of what it exactly is!

The angle of refraction causes white light to disperse. The process of refraction can be characterised as the blending of light as it flows from one medium to another. When light passes through a glass prism, it deviates twice: once when it enters the prism and again when it exits it. Because all the hues have various wavelengths and are refracted at different frequencies and angles, violet blends the best and red the least.

Rainbow is one of the best dispersion of light examples that can be comprehended similarly. We get to see the rainbow on rainy days when there are raindrops in the air and sunlight. When white sunlight enters raindrops, it is refracted, forming an arc of seven colour components on the sky’s surface. The sun’s white light is reflected by the raindrops, which act as a glass prism.

Cauchy’s formula provides a good understanding of the dispersion process. The formula states that the refractive index and wavelength of light have a phenomenological relationship. As a result, dispersion is caused by the refractive index n, which is proportional to the wavelength of light.

n= A+ B/ λ2

Where n is the refractive index, λ is the wavelength, and A and B are constants calculated for the material by plugging refractive indices at known wavelengths into the equation. To put it another way, the refractive index is inversely proportional to the square of light wavelength—the greater the value of the Refractive index, the smaller the wavelength value. As a result, ‘n’ is greatest for violet and least for red, indicating that violet has the most dispersion and red has the least.

Important Things to Remember

• A prism is a solid glass shape with two triangular bases and three rectangle bases.

• Dispersion of light is the phenomenon of white light splitting into different colours as it passes through a transparent medium, and spectrum is the pattern in which these seven colour components appear as they pass through the prism.

• The seven emerging hues emerge in the VIBGYOR (from top to bottom) order as a result of dispersion through the glass prism. VIBGYOR stands for Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

• The angle of refraction causes white light to disperse. The process of refraction is defined as the bending of light as it flows from one medium to another.

• When light passes through a glass prism, it deviates twice: once when it enters the prism and again when it exits it.

• Since all colours have various wavelengths and are refracted at different frequencies and angles, the Violet colour mixes the best and the red colour the least.

Conclusion 

Light dispersion occurs when white light is broken down into its constituent colours as a result of the refractive index of the surface and the wavelength of the light.

We’ve learned about prism dispersion, dispersion of light by a prism, the reasons for dispersion, an experiment, and more. If you have a deep comprehension of the subject, you are more likely to do well in the exam.