![]() ![]() When light and surfaces interact, it results in either solely or a mix of refraction, reflection, absorption or diffraction. Laser diffraction is grounded in the relationship between light and surfaces (in our case particles). The scope for automation means modern particle size analysis can often be a matter of loading the sample and hitting a button, which is an exciting prospect for pharmaceutical companies looking to scale their research. Semisolid drugs have some of the properties of solids and some of the properties of liquids, so understanding the size of the particles they contain is crucial in knowing how each particular product should be delivered to the human body. One example of this is the efficacy of ‘semisolid’ drugs, that are often used in ointments, creams, gels or lotions. Recognised for its capacity to reproduce results and size range spanning five orders of magnitude, laser diffraction has emerged as the technique of choice throughout the pharmaceutical industry where examining particle size is crucial in determining the performance of a product or process. Over the last twenty years, laser diffraction has, to a large extent, replaced traditional methods of particle size analysis, such as sieving and sedimentation (a previously common practice for granular material). The Role of Laser Diffraction in Particle Analysis As a technique that measures particle size distribution for both wet and dry dispersions, it offers many advantages, including a high level of precision, fast response, high potential for the repetition of results, and a wide measurable particle diameter range. There is some point reflection, while most light scatters.Laser diffraction has emerged as one of the most important and effective techniques in the world of particle size analysis thanks to its fast, non-destructive properties, its suitability for a broad range of particle sizes, and its ability to be fully automated.a white rough-surfac cardboard, like artists mount card A diffusion surface creates an illuminated spot.No reflection, you will see most light as scattered.a painted matt black surface like a black board An absorbing surface minimises reflection.Examples when you shine a beam at different surfaces: This would create a bright spot of reflecting light around the point the light strikes. It may also reflect some light, and diffuse some light. It is a surface that might absorb some of the light energy (eg. The diagram below is a more realistic version of how light scatters on a diffusion surface.Ī partially absorbing, diffusing and reflecting surface might be white gloss paint. So you would see light coming off it only as a proportion of the total light striking the surface. In the studio, an effective diffusion surface scatters light in all directions. High reflection, low scatter – silver foil: reflector.Low reflection, high scatter – white card: diffuser.The amount of light reflected depends on the how well the surface reflects rather than diffuses. A percentage of the light may be reflected in a reduced specular reflection. The scattered light radiates from around the strike point. Some light coming off the surface you would see as diffused light. Some of the light, in reality, may be absorbed by the surface. Remember, the perfect diffusion reflection surface does not exist. Note: The diagram is only showing two dimensions – in reality the hemisphere is three dimensional around the light strike-point. In a diffusion reflection, you would see light reflected from a strike point in a hemisphere of illumination. It is not the best model of how a light beam reacts in reality. This model of diffusion is mainly of interest to physicists. Although the diagram is only two dimensional (2D) the light scatter forms a hemisphere (3D) around a light strike-point. The diagram shows you the way light is scattered by a perfect diffusion surface. The total light in the beam spreads over the whole illuminated space, thus reducing the amount hitting your eye. Your eye, fixed at one point, sees a reduced amount of light. This scatter occurs around the point the light strikes the diffusion surface. In a perfect diffusion reflection, all the light will form a hemisphere of illumination. This type of reflection occurs when an incident ray of light strikes a surface and the light is scattered. The devices that we might use to create scattered light are called diffusers. The process that scatters light is what we call diffusion. It is usually used to help soften light or can be directed so as to reduce harsh shadows. In photography, something that creates diffusion or diffused light is a device that evenly scatters the light from a light source. Diffusion diffusion reflection (the process of…) ![]()
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