Answer the question on the basis of passage given below:

Adsorption is the phenomenon of attracting and retaining the molecules of a substance on the surface of a solid resulting into a higher concentration on the surface than in the bulk. The variation in the amount of gas adsorbed by the adsorbent with pressure at constant temperature is expressed as isotherm. A catalyst is a substance, when adsorbed enhances the rate of a chemical reaction without itself getting used up in the reaction. Depending on the type of the particles of the dispersed phase, colloids are classified as multimolecular, macromolecular and associated colloids and soap is such an example of associated colloids. Colloids show various properties such as Tyndall effect, colour, Brownian movement and charge development. There are positively charged sols and negatively charged sols. Due to this, electrophoresis and electroosmosis are shown by colloids.

Colloidal solutions illuminate the path of beam of light due to:

A. their range of diameter of particles between $10^{-9}$ to $10^{-6}$ m.
B. scattering of light
C. the formation of tyndall cone by a concave lens.
D. their clear solution.
E. large magnitude difference in the refractive indices of the dispersed phase and the dispersion medium.

Choose the correct answer from the options given below:

A, B and E only

The correct answer is Option (3) → A, B and E only.

Let us explore the illumination of a beam of light in colloidal solutions in detail, focusing on the key concepts of particle size, light scattering, and the Tyndall effect.

Colloidal Solutions

Colloidal solutions consist of a dispersed phase (tiny particles) and a dispersion medium (liquid or gas). The particles in a colloid are typically larger than those in a true solution but smaller than those in a suspension. They range in size from about \(10^{-9}\) meters (nanometers) to \(10^{-6}\) meters (micrometers).

Tyndall Effect

The visibility of a beam of light in a colloidal solution is primarily due to the Tyndall effect, which is the scattering of light by particles in a colloid. Here’s how it works:

Scattering of Light: When a beam of light passes through a colloidal solution, the particles scatter the light in various directions. This scattering occurs because the size of the colloidal particles is comparable to the wavelength of visible light (approximately \(400-700\) nanometers). The scattered light makes the path of the beam visible, creating a cone of light known as the Tyndall cone.

Factors Influencing Scattering: Several factors affect the scattering of light in colloidal solutions:

Size of Particles: The effectiveness of light scattering increases with the size of the particles, as larger particles scatter light more effectively than smaller ones. In colloids, particles that fall within the range of \(10^{-9}\) to \(10^{-6}\) meters can effectively scatter light.

Refractive Index Difference: The degree of scattering is also influenced by the difference in the refractive indices of the dispersed phase (the colloidal particles) and the dispersion medium (the solvent). When there is a large difference in refractive indices, more light is scattered, enhancing the visibility of the beam. This difference in refractive index can lead to stronger scattering and a more pronounced Tyndall effect

Characteristics of Colloids

Turbidity: Colloidal solutions are often not clear; they can appear cloudy or turbid due to the presence of dispersed particles. This is in contrast to true solutions, which are clear because the solute particles are at the molecular level and do not scatter light significantly.

Not Dependent on Lenses: While lenses can manipulate light, the formation of the Tyndall cone does not require a lens. The scattering occurs due to the presence of the colloidal particles themselves.

Summary of Options

A. Range of diameter of particles: Relevant because particle size influences scattering, but the key aspect is how scattering occurs.

B. Scattering of light: This is the core reason for the illumination of the beam and directly related to the Tyndall effect.

C. Formation of Tyndall cone by a concave lens: Incorrect, as the Tyndall effect does not depend on lens usage.

D. Clear solution: Incorrect because colloidal solutions are often turbid.

E. Large magnitude difference in refractive indices: This is a crucial factor that enhances light scattering, contributing to the visibility of the beam.

Conclusion
The illumination of a beam of light in colloidal solutions arises from the scattering of light by the colloidal particles, significantly influenced by the particle size and the difference in refractive indices of the dispersed phase and the medium. Therefore, the correct answer is A, B, and E only.