Which light source is commonly used in a nephelometer?

A HeNe (helium-neon) laser is commonly used in a nephelometer because it provides a coherent and monochromatic light source that can effectively illuminate the sample being analyzed. This is crucial for nephelometry, which measures the scattered light from particles suspended in a liquid. The laser's well-defined wavelength allows for precise measurements of the intensity of scattered light, which correlates to the concentration of particles in the solution.

In nephelometry, the quality of the light source significantly impacts the sensitivity and accuracy of the results. The coherent nature of laser light means that it travels in a well-defined direction, making it ideal for measuring small angles of scattered light, which is vital for detecting low concentrations of analytes.

Alternative light sources, such as incandescent lamps or LEDs, do not typically provide the same level of monochromaticity and coherence as lasers, leading to less accurate or sensitive measurements in nephelometric applications. Additionally, quartz lamps, while they might emit light in a broad spectrum, would also not match the precision and specificity offered by a HeNe laser. Therefore, the use of a HeNe laser in a nephelometer is essential for achieving optimal analytical performance.