Scattering of Light MCQs Quiz | Class 10

This quiz is designed for Class X students, focusing on the Science (Code 086) subject, specifically Unit III: Natural Phenomena. The topic covered is Scattering of Light, with a special emphasis on its applications in daily life (excluding the sun’s color at sunrise/sunset). Answer all 10 multiple-choice questions and click ‘Submit Quiz’ to see your score. You can then download an answer PDF for review.

Understanding Scattering of Light and its Applications

Scattering of light is a fascinating phenomenon where light rays deviate from a straight path after striking tiny particles of matter. The direction and intensity of scattered light depend on the wavelength of light and the size of the scattering particles. This phenomenon is responsible for many everyday observations around us.

Key Concepts in Scattering of Light

  • Rayleigh Scattering: Occurs when the size of the scattering particles is much smaller than the wavelength of light. In this type of scattering, the intensity of scattered light is inversely proportional to the fourth power of the wavelength (1/wavelength4). This means shorter wavelengths (like blue and violet) are scattered much more strongly than longer wavelengths (like red).
  • Tyndall Effect: The phenomenon of scattering of light by colloidal particles is known as the Tyndall effect. When a beam of light passes through a colloidal solution, the path of the light becomes visible due to the scattering of light by the larger colloidal particles.
  • Particle Size Dependence: If the scattering particles are much larger than the wavelength of light (e.g., dust, water droplets in clouds), all wavelengths are scattered almost equally, making the scattered light appear white.

Applications in Daily Life

Scattering of light plays a crucial role in explaining various natural phenomena:

  1. Why the Sky Appears Blue:

    The Earth’s atmosphere contains tiny air molecules (oxygen, nitrogen) which are much smaller than the wavelength of visible light. According to Rayleigh scattering, shorter wavelengths (blue and violet) are scattered much more efficiently than longer wavelengths (red, orange, yellow). When sunlight passes through the atmosphere, the blue light is scattered in all directions. Since our eyes are more sensitive to blue than violet, the sky appears blue. If there were no atmosphere, the sky would appear dark.

  2. Why Clouds Appear White:

    Clouds are made up of tiny water droplets and ice particles. These particles are typically much larger than the wavelength of visible light. When light encounters these larger particles, all wavelengths of visible light are scattered almost equally in all directions. This uniform scattering of all colors results in the clouds appearing white.

  3. Why Danger Signals are Red:

    Red light has the longest wavelength among visible light and is scattered the least by atmospheric particles like smoke and fog. This allows red light to travel the farthest through the atmosphere without significant scattering, making it clearly visible even from a distance or in adverse weather conditions. This property makes red the ideal color for danger signals, stop lights, and brake lights.

  4. Tyndall Effect in Action:

    You can observe the Tyndall effect when a beam of sunlight enters a dusty room through a small hole. The path of light becomes visible due to the scattering of light by the dust particles. Similarly, the headlights of a car passing through fog illuminate the path due to the scattering of light by the fog droplets.

  5. The Color of Deep Sea Water:

    When sunlight penetrates deep into the ocean, the longer wavelength colors (red, orange, yellow) are absorbed more readily by the water molecules. The shorter wavelength blue light, however, is scattered more effectively by the water molecules, similar to how the atmosphere scatters blue light. As a result, deep sea water appears blue.

Quick Revision Points

  • Scattering is the redirection of light by particles.
  • Rayleigh scattering depends strongly on wavelength (shorter wavelengths scatter more).
  • Particle size relative to wavelength determines scattering type.
  • Small particles scatter blue light more (blue sky).
  • Large particles scatter all colors equally (white clouds).
  • Red light scatters least, travels furthest (danger signals).
  • Tyndall effect makes light path visible in colloids.

Practice Questions

  1. What phenomenon explains why the sky often appears blue during the day?
  2. Why are traffic stop lights and danger signals typically red?
  3. What is the primary reason that clouds generally appear white?
  4. When does Rayleigh scattering predominantly occur, based on particle size relative to wavelength?
  5. Name an effect where the path of a light beam becomes visible due to scattering by colloidal particles.