![]() Gas and solid samples require specialized instruments or accessories for accurate refractive index measurement. When using a digital refractometer, liquids and semi-liquid samples can be measured with high accuracy (e.g. Refractive index values can also be determined for gases. Refractive index measurement checks the purity and concentration of liquid, semi-liquid and solid samples. Due to the fact that it is a widely available, reliable and stable light source, the sodium D-line has long been used in the study of refractive index. To generate a defined wavelength, refractometers most often use the sodium D-line, which corresponds to 589.3 nm. However, for industrial applications where refractive index measurement is required, it is necessary to have a defined, precise wavelength to allow the refractive index measurement of different samples to be analyzed under the same conditions for quality control. This relationship is represented by the equation: This means the greater the wavelength, the lower the refractive index. Therefore, the refractive index ( n) is inversely proportional to the wavelength and also to the speed of light. Where λ 0 is the wavelength of that light in a vacuum (or air). Similarly, the wavelength in the same medium is: We know that the speed of light in a medium is:Ĭ is the speed of light in a vacuum (or air) ![]() This dispersion relation can be calculated as follows. Almost all substances have different refractive indices that also differ depending on the wavelength used. In a refractive index measurement, the wavelength of the light beam matters because of the effect of dispersion on the properties of waves in a medium (known as dispersion relation). This ensures a fast and accurate determination of the refractive index value. Older instruments such as Abbe refractometers may require a water bath to control the temperature, while many modern, digital refractometers use Peltier elements to control the system temperature. Therefore, temperature must be accurately measured and, if possible, controlled. In other words, the higher the temperature, the lower the refractive index, as shown in the graph below which uses water as the sample medium.Īs you can see, the sample temperature has a major influence on the measurement procedure. If a medium is less optically dense due to a temperature increase, the light will travel faster, which causes the deflected angle to shift slightly. Atomic vibration increases as temperature increases, which causes the atoms to move farther apart and reduces the optical density value of the sample medium.Īs noted previously, the refractive index describes how fast a light beam travels through media. Temperature influences the space in which atoms fit together to create a molecule. So what is the relationship between refractive index determination and temperature?įirst, we need to understand the effect of temperature on a liquid sample. User skills and knowledge (theory of applications, technologies, methods, tips and tricks).Time reduction quick adjustment and scalability of methods.Sustainable design (futureproof modular design long lasting).Shift to the next level measurement process (from manual to automated, or to on-line measurement automation). ![]() Reduction in operating costs Total cost of ownership Maintenance cost reduction.Productivity (released time from the team) Uptime Optimize processes.Preventive maintenance Minimize downtime.Connectivity Software solutions Data flow from one instrument to another.
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