Dispersion of Light MCQs Quiz | Class 10

This quiz on Dispersion of Light for Class X Science (Code 086) covers Unit III: Natural Phenomena, focusing on key concepts like spectrum formation and the VIBGYOR sequence. Test your understanding, then submit to see your score and download a detailed answer PDF.

Understanding Dispersion of Light

Dispersion of light is a fascinating phenomenon where white light splits into its constituent colors when passing through a transparent medium, such as a prism. This separation occurs because different colors of light travel at slightly different speeds in the medium, causing them to bend (refract) at different angles.

Spectrum Formation

When a beam of white light, like sunlight, passes through a glass prism, it is dispersed into a band of seven colors. This band of colors is called the spectrum. Isaac Newton was the first to demonstrate that white light is composed of seven distinct colors. He showed that when white light passes through a prism, it separates into these colors, and when these colors are passed through an identical inverted prism, they recombine to form white light again.

The order of colors in the spectrum is fixed and can be remembered by the acronym VIBGYOR:

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

Red light, having the longest wavelength among the visible colors, deviates the least, while violet light, with the shortest wavelength, deviates the most. This difference in deviation is due to the refractive index of the prism material being slightly different for different wavelengths (colors) of light. For a given medium, the refractive index is generally greater for shorter wavelengths and smaller for longer wavelengths.

Key Concepts Related to Dispersion

  • White Light Composition: White light is a mixture of various colors, each with its own specific wavelength.
  • Refraction and Wavelength: The extent to which a light ray bends upon entering a new medium depends on its wavelength. Shorter wavelengths bend more.
  • Prism’s Role: A prism acts as a disperser, separating the colors due to their differing refractive indices.
  • VIBGYOR Sequence: The fixed order of colors from least deviated (Red) to most deviated (Violet).
  • Real-world Examples: Rainbows are a natural phenomenon of light dispersion and total internal reflection by water droplets in the atmosphere.

Quick Revision

  • Dispersion is the splitting of white light into its constituent colors.
  • A prism is used to demonstrate dispersion.
  • The spectrum consists of VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red).
  • Violet light deviates the most (shortest wavelength).
  • Red light deviates the least (longest wavelength).
  • Refractive index varies with wavelength, causing different bending for different colors.
  • Rainbows are formed due to dispersion, refraction, and total internal reflection of sunlight by raindrops.

Practice Questions

  1. What is the name of the phenomenon where white light splits into its seven constituent colors?
  2. Which color of light has the maximum speed in a vacuum, and how does its speed change in a prism compared to other colors?
  3. Explain why red light deviates less than violet light when passing through a prism.
  4. Describe the role of water droplets in the formation of a rainbow.
  5. If a beam of monochromatic light (light of a single color) passes through a prism, will it show dispersion? Justify your answer.