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Diffuse Sky Radiation
Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattering, scattered from the direct solar beam by molecules or particulates in the Earth's atmosphere, atmosphere. It is also called sky radiation, the determinative process for changing the colors of the sky. Approximately 23% of direct incident radiation of total sunlight is removed from the direct solar beam by scattering into the atmosphere; of this amount (of incident radiation) about two-thirds ultimately reaches the earth as photon diffusion, photon diffused skylight radiation. The dominant radiative scattering processes in the atmosphere are Rayleigh scattering and Mie scattering; they are elastic scattering, elastic, meaning that a photon of light can be deviated from its path without being absorbed and without changing wavelength. Under an overcast sky, there is no direct sunlight, and all light results from diffused skylight radiation. Proceeding from analyses of the afterm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rayleigh Sunlight Scattering
Rayleigh may refer to: Science *Rayleigh scattering * Rayleigh–Jeans law *Rayleigh waves *Rayleigh (unit), a unit of photon flux named after the 4th Baron Rayleigh *Rayl, rayl or Rayleigh, two units of specific acoustic impedance and characteristic acoustic impedance, named after the 3rd Baron Rayleigh *Rayleigh criterion in angular resolution *Rayleigh distribution *Rayleigh fading * Rayleigh law on low-field magnetization *Rayleigh length *Rayleigh number, a dimensionless number for a fluid associated with buoyancy driven flow *Rayleigh quotient * Rayleigh–Ritz method *Plateau–Rayleigh instability explains why a falling stream of fluid breaks up into smaller packets *Rayleigh–Taylor instability an instability of an interface between two fluids Title of nobility *Baron Rayleigh **Charlotte Mary Gertrude Strutt, 1st Baroness Rayleigh **John William Strutt, 3rd Baron Rayleigh, physicist, winner of a Nobel Prize in 1904 **Robert John Strutt, 4th Baron Rayleigh, physicist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanometer
330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling Despite the various list of dialects of English, English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English orthography, the two most notable variati ...), is a units of measurement, unit of length in the International System of Units (SI), equal to one billionth (short scale) or one thousand million (long scale) of a metre, meter (0.000000001 m) and to 1000 picometres. One nanometre can be expressed in scientific notation as 1 × 10−9 m and as m. History The nanometre was formerly known as the "''millimicrometre''" – or, more commonly, the "''millimicron''" for short – since it is of a micrometre, micrometer. It was often de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zenith
The zenith (, ) is the imaginary point on the celestial sphere directly "above" a particular location. "Above" means in the vertical direction (Vertical and horizontal, plumb line) opposite to the gravity direction at that location (nadir). The zenith is the "highest" point on the celestial sphere. The direction opposite of the zenith is the nadir. Origin The word ''zenith'' derives from an inaccurate reading of the Arabic language, Arabic expression (), meaning "direction of the head" or "path above the head", by Medieval Latin scribes in the Middle Ages (during the 14th century), possibly through Old Spanish. It was reduced to ''samt'' ("direction") and miswritten as ''senit''/''cenit'', the ''m'' being misread as ''ni''. Through the Old French ''cenith'', ''zenith'' first appeared in the 17th century. Relevance and use The term ''zenith'' sometimes means the culmination, highest point, way, or level reached by a celestial body on its daily apparent path around a given poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Path Length
In optics, optical path length (OPL, denoted ''Λ'' in equations), also known as optical length or optical distance, is the length that light needs to travel through a vacuum to create the same phase difference as it would have when traveling through a given medium. It is calculated by taking the product of the geometric length of the optical path followed by light and the refractive index of the homogeneous medium through which the light ray propagates; for inhomogeneous optical media, the product above is generalized as a path integral as part of the ray tracing procedure. A difference in OPL between two paths is often called the optical path difference (OPD). OPL and OPD are important because they determine the phase of the light and govern interference and diffraction of light as it propagates. In a medium of constant refractive index, ''n'', the OPL for a path of geometrical length ''s'' is just :\mathrm = n s .\, If the refractive index varies along the path, the OPL is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Mass (astronomy)
In astronomy, air mass or airmass is a measure of the amount of air along the line of sight when observing a star or other celestial source from below Earth's atmosphere . It is formulated as the integral of air density along the ray (optics), light ray. As it penetrates the atmosphere, light is attenuated by light scattering by particles, scattering and absorption (electromagnetic radiation), absorption; the thicker atmosphere through which it passes, the greater the attenuation. Consequently, astronomical object, celestial bodies when nearer the horizon appear less bright than when nearer the zenith. This attenuation, known as extinction (astronomy)#Atmospheric extinction, atmospheric extinction, is described quantitatively by the Beer–Lambert law. "Air mass" normally indicates ''relative air mass'', the ratio of absolute air masses (as defined above) at oblique incidence relative to that at zenith. So, by definition, the relative air mass at the zenith is 1. Air mass increas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Path
Optical path (OP) is the trajectory that a light ray follows as it propagates through an optical medium. The geometrical optical-path length or simply geometrical path length (GPD) is the length of a segment in a given OP, i.e., the Euclidean distance integrated along a ray between any two points. The mechanical length of an optical device can be reduced to less than the GPD by using folded optics. The '' optical path length'' in a homogeneous medium is the GPD multiplied by the refractive index of the medium. Factors affecting optical path Path of light in medium, or between two media is affected by the following: * Reflection ** Total internal reflection * Refraction * Dispersion of light * Absorption Simple materials used * Lenses * Prisms * Mirror A mirror, also known as a looking glass, is an object that Reflection (physics), reflects an image. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tangent Lines To Circles
In Euclidean geometry, Euclidean plane geometry, a tangent line to a circle is a Line (geometry), line that touches the circle at exactly one Point (geometry), point, never entering the circle's interior. Tangent lines to circles form the subject of several theorems, and play an important role in many geometrical Compass and straightedge constructions, constructions and Mathematical proof, proofs. Since the tangent, tangent line to a circle at a Point (geometry), point is perpendicular to the radius to that point, theorems involving tangent lines often involve radial lines and orthogonality, orthogonal circles. Tangent lines to one circle A tangent line to a circle Line-line intersection, intersects the circle at a single point . For comparison, secant lines intersect a circle at two points, whereas another line may not intersect a circle at all. This property of tangent lines is preserved under many geometrical Transformation (geometry), transformations, such as scaling (g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunset
Sunset (or sundown) is the disappearance of the Sun at the end of the Sun path, below the horizon of the Earth (or any other astronomical object in the Solar System) due to its Earth's rotation, rotation. As viewed from everywhere on Earth, it is a phenomenon that happens approximately once every 24 hours, except in areas close to the Geographical pole, poles. The equinox Sun sets due west at the moment of both the spring and autumn equinoxes. As viewed from the Northern Hemisphere, the Sun sets to the northwest (or not at all) in the spring and summer, and to the southwest in the autumn and winter; these seasons are reversed for the Southern Hemisphere. The sunset is defined in astronomy the moment the upper limb of the Sun disappears below the horizon. Near the horizon, atmospheric refraction causes sunlight rays to be distorted to such an extent that geometrically the solar disk is already about one diameter below the horizon when a sunset is observed. Sunset is distinct from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunrise
Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning, at the start of the Sun path. The term can also refer to the entire process of the solar disk crossing the horizon. Terminology Although the Sun appears to "rise" from the horizon, it is actually the ''Earth's'' motion that causes the Sun to appear. The illusion of a moving Sun results from Earth observers being in a rotating reference frame; this apparent motion caused many cultures to have mythologies and religions built around the geocentric model, which prevailed until astronomer Nicolaus Copernicus formulated his heliocentric model in the 16th century. Architect Buckminster Fuller proposed the terms "sunsight" and "sunclipse" to better represent the heliocentric model, though the terms have not entered into common language. Astronomically, sunrise occurs for only an instant, namely the moment at which the upper limb of the Sun appears tangent to the horizon. However, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geometric Optics
Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician who works in the field of geometry is called a '' geometer''. Until the 19th century, geometry was almost exclusively devoted to Euclidean geometry, which includes the notions of point, line, plane, distance, angle, surface, and curve, as fundamental concepts. Originally developed to model the physical world, geometry has applications in almost all sciences, and also in art, architecture, and other activities that are related to graphics. Geometry also has applications in areas of mathematics that are apparently unrelated. For example, methods of algebraic geometry are fundamental in Wiles's proof of Fermat's Last Theorem, a problem that was stated in terms of elementary arithmetic, and remained unsolved for several centuries. Duri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Size
Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles ('' bubbles''). The notion of particle size applies to particles in colloids, in ecology, in granular material (whether airborne or not), and to particles that form a granular material (see also grain size). Measurement There are several methods for measuring particle size and particle size distribution. Some of them are based on light, other on ultrasound,Dukhin, A. S. and Goetz, P. J. ''Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound'', Elsevier, 2017 or electric field, or gravity, or centrifugation. The use of sieves is a common measurement technique, however this process can be more susceptible to human error and is time consuming. Technology such as dynamic image analysis (DIA) can make particle size distribution analyses much easier. This approach can be seen in instruments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a Transmission medium, medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates. Hearing protection device, Hearing protectors help reduce Sound power, acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs). In electrical engineering and telecommunications, attenuation affects the Wave propagation, propagation of waves and signals in electrical circuits, in optical fibers, and in air. Attenuator (electronics), Electrical attenuators and optical attenuators are commonly manufactured components in this field. Background In many cases, attenuation is an exponential function of the path length through the medium. In optics and in chemical spectroscopy, this is known as the Beer–Lambert law. In engineering, attenu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
