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Background In white populations, computed tomographic measurements of coronary-artery calcium predict coronary heart disease independently of traditional coronary. Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of. We report studies on the synthesis of gold nanorods by a three-step seeding protocol method using a variety of different gold seeds. The synthetic method is adapted.

Optics includes study of of light. Optics is the branch of which involves the behaviour and properties of, including its interactions with and the construction of that use or it. Optics usually describes the behaviour of,, and light. Because light is an, other forms of such as,, and exhibit similar properties. Most optical phenomena can be accounted for using the description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models.

The most common of these,, treats light as a collection of that travel in straight lines and bend when they pass through or reflect from surfaces. Is a more comprehensive model of light, which includes effects such as and that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation. Some phenomena depend on the fact that light has both.

Explanation of these effects requires. When considering light's particle-like properties, the light is modelled as a collection of particles called '. Deals with the application of quantum mechanics to optical systems. Optical science is relevant to and studied in many related disciplines including, various fields,, and (particularly and ). Practical applications of optics are found in a variety of technologies and everyday objects, including,,,,, and.

The Nimrud lens Optics began with the development of lenses by the and. The earliest known lenses, made from polished crystal, often, date from as early as 700 BC for lenses such as the Layard/. The and filled glass spheres with water to make lenses. These practical developments were followed by the development of theories of light and vision by ancient and philosophers, and the development of in the. The word optics comes from the word ὀπτική ( optikē), meaning 'appearance, look'.

On optics broke down into two opposing theories on how vision worked, the ' and the. The intro-mission approach saw vision as coming from objects casting off copies of themselves (called eidola) that were captured by the eye. With many propagators including,, and their followers, this theory seems to have some contact with modern theories of what vision really is, but it remained only speculation lacking any experimental foundation. First articulated the emission theory, the idea that is accomplished by rays emitted by the eyes. He also commented on the reversal of mirrors in.

Some hundred years later, wrote a treatise entitled where he linked vision to, creating geometrical optics. He based his work on Plato's emission theory wherein he described the mathematical rules of and described the effects of qualitatively, although he questioned that a beam of light from the eye could instantaneously light up the stars every time someone blinked., in his treatise, held an extramission-intromission theory of vision: the rays (or flux) from the eye formed a cone, the vertex being within the eye, and the base defining the visual field. The rays were sensitive, and conveyed information back to the observer’s intellect about the distance and orientation of surfaces. He summarised much of Euclid and went on to describe a way to measure the, though he failed to notice the empirical relationship between it and the angle of incidence. Reproduction of a page of 's manuscript showing his knowledge of.

During the, Greek ideas about optics were resurrected and extended by writers in the. Dreamfall No Dvd Cracks. One of the earliest of these was (c. 801–73) who wrote on the merits of Aristotelian and Euclidean ideas of optics, favouring the emission theory since it could better quantify optical phenomena.

In 984, the mathematician wrote the treatise 'On burning mirrors and lenses', correctly describing a law of refraction equivalent to. He used this law to compute optimum shapes for lenses and. In the early 11th century, (Ibn al-Haytham) wrote the ( Kitab al-manazir) in which he explored reflection and refraction and proposed a new system for explaining vision and light based on observation and experiment.