Nephelometry is based on the measurement of light that is:

• A. Absorbed
• B. Reflected
• C. Transmitted
• D. Adsorbed by the particles of a suspension

Answer: (B)

Nephelometry hinges on how much light is scattered by particles in a suspension rather than how much is absorbed or transmitted. When the light beam enters the sample, particles deflect some of it away from the original path. The detector positioned at a fixed angle captures this scattered light; the amount detected increases with particle concentration and size, providing a measure of turbidity due to the suspended particles. Absorbed light is the domain of absorption-based methods, transmitted light is what passes through the sample, and adsorbed describes sticking to surfaces rather than scattering within the suspension. Thus, the signal comes from light that is scattered (often referred to as reflected) by the particles.