Which phenomenon is used to identify a colloid by scattering light?

Which phenomenon is used to identify a colloid by scattering light?

• A. The absorption of light by solvent molecules.
• B. The diffusion of solute particles.
• C. The scattering of light by colloid particles.
• D. The reflection of light by a surface.

Answer: (C)

Light scattering by dispersed particles in a colloid is the key idea being tested. When a beam of light passes through a colloidal mixture, the particles are large enough to scatter some of the light in different directions, making the beam visible as it travels through the medium. This scattering, the Tyndall effect, occurs because the colloidal particles have sizes comparable to the wavelength of visible light and are present throughout the continuous phase, unlike true solutions where particles are too small to scatter light appreciably. This optical signature helps distinguish colloids from true solutions, which do not show noticeable light scattering. The other options describe processes that don’t reveal dispersed particles via light interactions: absorption by solvent molecules doesn’t indicate colloids; diffusion is about particle movement rather than light scattering; reflection by a surface is just light bouncing off a boundary and doesn’t probe the interior scattering behavior of the medium.

Light scattering by dispersed particles in a colloid is the key idea being tested. When a beam of light passes through a colloidal mixture, the particles are large enough to scatter some of the light in different directions, making the beam visible as it travels through the medium. This scattering, the Tyndall effect, occurs because the colloidal particles have sizes comparable to the wavelength of visible light and are present throughout the continuous phase, unlike true solutions where particles are too small to scatter light appreciably. This optical signature helps distinguish colloids from true solutions, which do not show noticeable light scattering. The other options describe processes that don’t reveal dispersed particles via light interactions: absorption by solvent molecules doesn’t indicate colloids; diffusion is about particle movement rather than light scattering; reflection by a surface is just light bouncing off a boundary and doesn’t probe the interior scattering behavior of the medium.