What is dispersion of light?

Short Answer

Dispersion of light is the process in which white light splits into its seven colours when it passes through a prism or any transparent medium. This happens because each colour of light bends by a different amount while moving through the medium. As a result, the colours spread out to form a spectrum.

We observe dispersion in nature in the form of a rainbow. When sunlight enters raindrops, the light bends and splits into different colours. Dispersion is important in understanding colour formation, prisms, and various optical phenomena.

Detailed Explanation :

Dispersion of Light

Dispersion of light is an important concept in optics that explains how white light separates into its different colours. White light, such as sunlight, is not made of a single colour. Instead, it contains seven distinct colours: violet, indigo, blue, green, yellow, orange, and red (VIBGYOR). These colours combine to appear white to our eyes. When white light passes through a transparent medium like a glass prism, these colours bend by different amounts and spread out. This spreading and separation of colours is called dispersion.

Dispersion tells us that different colours of light have different wavelengths. Violet light has the shortest wavelength, while red light has the longest. Because of this difference, each colour bends differently when passing from one medium to another. This bending helps separate the colours and form a beautiful spectrum.

The study of dispersion helps us understand natural activities like rainbows and human-made tools such as prisms, projectors, and spectrometers. Without dispersion, we would not be able to see the colourful world created by white light.

How Dispersion Occurs

To understand dispersion, it is important to know what happens when light enters a prism or another transparent object. When light travels from air into glass, its speed decreases. But this slowing does not happen equally for all colours. Each colour of light travels at a slightly different speed inside the medium.

Because speed changes differently for each colour, the amount of bending during refraction also changes. Violet light slows down the most and bends the most. Red light slows down the least and bends the least. The remaining colours bend in between these two.

So, when white light enters a prism:

  1. Each colour bends at a different angle.
  2. The colours spread out.
  3. On exiting the prism, they separate clearly to form a spectrum.

This complete process is known as dispersion of light.

Colours and Their Bending

The order of colours in the spectrum is always the same: violet at one end and red at the other. The bending decreases from violet to red. The colours appear in the following sequence:

  • Violet: bends the most
  • Indigo
  • Blue
  • Green
  • Yellow
  • Orange
  • Red: bends the least

This fixed pattern occurs because each colour has a different wavelength and refractive index inside the prism.

Dispersion in Nature

Dispersion is not limited to laboratory experiments. It occurs naturally around us. The most beautiful example of dispersion in nature is a rainbow.

Rainbow Formation:
Rainbows form when sunlight enters water droplets in the atmosphere. Each droplet acts like a tiny prism. Light refracts, disperses into seven colours, reflects internally in the droplet, and then refracts again when leaving. All these steps together form a colourful arc across the sky.

Other natural dispersion examples include:

  • Colourful patterns on soap bubbles
  • Colours on oil films floating on water
  • Shining colours seen on CD surfaces

All these effects are caused by bending and spreading of light.

Importance of Dispersion

Dispersion plays a major role in optics and many scientific applications:

  1. Spectroscopy:
    Scientists use dispersion to study the composition of stars and gases. The spectrum reveals what elements are present.
  2. Optical Instruments:
    Prisms and diffraction devices use dispersion to separate colours. These are used in laboratories and industries.
  3. Communication Technology:
    Optical fibres work with different wavelengths of light. Understanding dispersion helps improve data transmission.
  4. Designing Lenses:
    Dispersion affects how lenses focus light. Engineers use this knowledge to reduce colour distortion in cameras, telescopes, and microscopes.
  5. Everyday Life:
    The colours we see in nature, design lighting, and artistic effects are based on dispersion principles.

Why Dispersion Happens

Dispersion occurs because different colours of light travel at different speeds in a medium. A single ray of white light contains many wavelengths. When these wavelengths enter a transparent medium, each bends by a different amount. Because of this uneven bending, the colours spread out and separate.

This simple idea explains complex events in nature and helps in advanced scientific studies.

Conclusion

Dispersion of light is the splitting of white light into its seven colours when it passes through a transparent medium like a prism. It happens because different colours bend differently due to varying wavelengths and speeds. Dispersion explains natural wonders like rainbows and supports many optical technologies. Understanding dispersion helps us appreciate how white light creates the colourful world we see.