![]() ![]() The refractive index difference between the particle and the surrounding medium is infinite.Particles of all sizes scatter light with the same efficiency.Light is scattered only at narrow angles.The particles being measured are opaque discs.It is recommended that 10x the laser wavelength is the minimum for this approximation. The particle size must be relatively large.It provides a simpler approach by additionally assuming that: The Fraunhofer approximation of the Mie theory was a much easier model to use and was therefore widely adopted at this stage. In the late 1970s, when laser diffraction systems were first introduced, limited computing power made it difficult, and impractical, to rigorously apply Mie theory. The Mie scattering theory and the Fraunhofer diffraction approximation are two key theories used to calculate the type of light intensity distribution patterns produced by particles of various sizes. Laser diffraction relies on optical models to help scientists understand data produced. Speak with the ATA Scientific team today to get expert advice on the right instruments for your research Request free consultation Laser Diffraction Models Looking for the perfect analytics instrument for YOUR next big discovery? These angular scattering patterns are measured with various specially-designed detectors and particle size distribution is determined from the resulting data. During a laser diffraction experiment, particles are illuminated in a collimated laser beam – producing a scattered pattern of light – allowing scientists to deduce particle size and shape.Īs a general rule, the bigger particles will bring about a high intensity of scattering at low angles to the beam and the smaller particles, on the other hand, create a low-intensity signal at far wider angles. Ensemble techniques use a broadened beam of laser light which scatters the light on to a specialised lens to offer a greater collection. Laser diffraction is what is known as a ‘cloud’ or ‘ensemble’ technique meaning it offers a result for the entire sample, as opposed to providing information for individual particles. Detectors – Specialised detectors (typically an array of photo-sensitive silicon diodes) are applied to measure the light pattern produced across a range of angles.A sample presentation system – This ensures that the material being tested successfully travels through the laser beam as a stream of particles that have a known state of dispersion and can be reproduced. ![]()
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