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Light and Shadows
Published in Abdul Al-Azzawi, Light and Optics, 2018
Any dark object absorbs some wavelengths of light, as discussed in the properties of light in Chapter 1. A black object absorbs nearly all of the visible light wavelengths when they are incident on it. Light that is not absorbed when incident upon an object is either transmitted or reflected. If all light incident upon an object is transmitted, the object is called transmissive. If all light incident upon an object is reflected or absorbed, the object is called opaque. Since light cannot pass through an opaque object, a shadow will be produced in the space behind the object. The shadow formed by a point source S of light is shown in Figure 2.2. Since light is propagated in straight lines, rays drawn from the point source past the edges of the opaque object form a sharp shadow. The shape of the shadow is proportional to the shape of the object. The shape of the shadow depends on the opaque object location relative to the point source. The region in which no light has entered is called the umbra.
Light and Shadows
Published in Abdul Al-Azzawi, Photonics, 2017
Any dark object absorbs some wavelengths of light, as discussed in the properties of light in Chapter 1. A black object absorbs nearly all of the visible light wavelengths when they are incident on it. Light that is not absorbed when incident upon an object is either transmitted or reflected. If all light incident upon an object is transmitted, the object is called transmissive. If all light incident upon an object is reflected or absorbed, the object is called opaque. Since light cannot pass through an opaque object, a shadow will be produced in the space behind the object. The shadow formed by a point source S of light is shown in Figure 2.2. Since light is propagated in straight lines, rays drawn from the point source past the edges of the opaque object form a sharp shadow. The shape of the shadow is proportional to the shape of the object. The shape of the shadow depends on the opaque object location relative to the point source. The region in which no light has entered is called the umbra.
Analysis of 18th century glass beads with X-ray computed microtomography
Published in Vladimir Litvinenko, Innovation-Based Development of the Mineral Resources Sector: Challenges and Prospects, 2018
A.Y. Ramdani, T. Schlothauer, G. Heide, V.S. Nikiforova, I.V. Talovina
Several kinds of opacifiers have been used throughout history. The most ancient is Calcium antimonate giving a white color and lead antimonate giving a yellow color (Lahlil et al., 2008). The addition of Antimony and calcium oxide will produce calcium antimonate which precipitates in the cooling glass, making it white and opaque. Other types of opacifiers were tin dioxide from cassiterite, typically used in Venetian glasses, and apatite (Moretti and Hreglich, 2012). The opacifying effect is due to small crystals or air bubbles dispersed in the glass matrix. Their presence in glass will reflect the wavelengths of light and make the glass opaque, while in a translucent or transparent glass, light will be transmitted (Henderson, 2013).
Compatibility and efficacy of vaporised hydrogen peroxide technology to decontaminate reusable personal protective equipment
Published in Cogent Engineering, 2022
Daniela Rondinone, Tautvydas Karitonas, Enrico Allegra
The opacity meter measures how much light is reflected through a material. The reflection of light is measured by placing an absolute white and absolute black working board behind a surface/material, and from this the degree of reflection is determined mathematically by the device. The outcome of the opacity measurement is a numerical value that can be used to assess the degree of opaqueness as follows: a 0 reading means the material is fully transparent, and a 100 reading means the material is fully opaque.