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Surface Vertex

In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the focal points, the principal points, and the nodal points.[1] For ideal systems, the basic imaging properties such as image size, location, and orientation are completely determined by the locations of the cardinal points; in fact only four points are necessary: the focal points and either the principal or nodal points. The only ideal system that has been achieved in practice is the plane mirror,[2] however the cardinal points are widely used to approximate the behavior of real optical systems
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Optical Cavity
An optical cavity, resonating cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light. They are also used in optical parametric oscillators and some interferometers. Light confined in the cavity reflects multiple times, producing standing waves for certain resonance frequencies. The standing wave patterns produced are called modes; longitudinal modes differ only in frequency while transverse modes differ for different frequencies and have different intensity patterns across the cross-section of the beam. Different resonator types are distinguished by the focal lengths of the two mirrors and the distance between them. Flat mirrors are not often used because of the difficulty of aligning them to the needed precision
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Robert Campin
Robert Campin (c. 1375 – 26 April 1444), now usually identified with the Master of Flémalle (earlier the Master of the Merode Triptych, before the discovery of three other similar panels[1]), was the first great master of Flemish and Early Netherlandish painting. Campin's identity and the attribution of the paintings in both the "Campin" and "Master of Flémalle" groupings have been a matter of controversy for decades. Campin was highly successful during his lifetime, and thus his activities are relatively well documented,[2] but he did not sign or date his works, and none can be confidently connected with him. A corpus of work is attached to the unidentified "Master of Flémalle,"[3][4] so named in the 19th century after three religious panels said to have come from a monastery in Flémalle
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Ray (optics)
In optics a ray is an idealized model of light, obtained by choosing a line that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow.[1][2] Rays are used to model the propagation of light through an optical system, by dividing the real light field up into discrete rays that can be computationally propagated through the system by the techniques of ray tracing. This allows even very complex optical systems to be analyzed mathematically or simulated by computer. Ray tracing uses approximate solutions to Maxwell's equations that are valid as long as the light waves propagate through and around objects whose dimensions are much greater than the light's wavelength. Ray theory (geometrical optics) does not describe phenomena such as diffraction, which require wave theory
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Flashlight
A flashlight (US) or torch (UK) is a portable hand-held electric light. The source of the light often used to be an incandescent light bulb (lamp) but has been gradually replaced by light-emitting diodes (LEDs) since the mid-2000s. A typical flashlight consists of the light source mounted in a reflector, a transparent cover (sometimes combined with a lens) to protect the light source and reflector, a battery, and a switch. These are supported and protected by a case. The invention of the dry cell and miniature incandescent electric lamps made the first battery-powered flashlights possible around 1899. Today, flashlights use mostly light-emitting diodes and run on disposable or rechargeable batteries. Some are powered by the user turning a crank, shaking the lamp, or squeezing it
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Headlamp

A headlamp is a lamp attached to the front of a vehicle to illuminate the road ahead. Headlamps are also often called headlights, but in the most precise usage, headlamp is the term for the device itself and headlight is the term for the beam of light produced and distributed by the device. Headlamp performance has steadily improved throughout the automobile age, spurred by the great disparity between daytime and nighttime traffic fatalities: the US National Highway Traffic Safety Administration states that nearly half of all traffic-related fatalities occur in the dark, despite only 25% of traffic travelling during darkness.[1] Other vehicles, such as trains and aircraft, are required to have headlamps. Bicycle headlamps are often used on bicycles, and are required in some jurisdictions
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Spotlight (theatre Lighting)
A spotlight (or followspot) is a powerful stage lighting instrument which projects a bright beam of light onto a performance space. Spotlights are controlled by a spotlight operator who tracks actors around the stage. Spotlights are most commonly used in concerts, musicals and large scale presentations where highlighting a specific mobile individual is critical. Spotlights are sometimes located overhead on catwalks. In some theatres, they may also be located in the control booth or purposely built "spot booths" in addition to the catwalk. Spotlights may be arranged in a variety of patterns for coverage. For example, they can be located to the back or rear of a theater and aimed at the stage in front of them. This location can become problematic due to the audience being distracted by fan noise or the spot operator speaking into their headset microphone. In circus and sports, spotlights may be arranged around the facility covering both sides and the ends
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Concentrated Solar Power

Concentrated solar power (CSP, also known as concentrating solar power, concentrated solar thermal) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight onto a receiver.[2] Electricity is generated when the concentrated light is converted to heat (solar thermal energy), which drives a heat engine (usually a steam turbine) connected to an electrical power generator[3][4][5] or powers a thermochemical reaction.[6][7][8] CSP had a global total installed capacity of 5,500 MW in 2018, up from 354 MW in 2005. Spain accounted for almost half of the world's capacity, at 2,300 MW, despite no new capacity entering commercial operation in the country since 2013.[9] The United States follows with 1,740 MW. Interest is also notable in North Africa and the Middle East, as well as India and China
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Computer Monitor
A computer monitor is an output device that displays information in pictorial form. A monitor usually comprises the visual display, circuitry, casing, and power supply. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) with LED backlighting having replaced cold-cathode fluorescent lamp (CCFL) backlighting. Older monitors used a cathode ray tube (CRT). Monitors are connected to the computer via VGA, Digital Visual Interface (DVI), HDMI, DisplayPort, Thunderbolt, low-voltage differential signaling (LVDS) or other proprietary connectors and signals. Originally, computer monitors were used for data processing while television sets were used for entertainment. From the 1980s onwards, computers (and their monitors) have been used for both data processing and entertainment, while televisions have implemented some computer functionality
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Dental Mirror
A mouth mirror or dentist's mirror is an instrument used in dentistry. The head of the mirror is usually round, and the most common sizes used are the No. 4 Ø (18 mm) and No. 5 (Ø 20 mm).[1] A No. 2 is sometimes used when a smaller mirror is needed, such as when working on back teeth with a dental dam in place. The mouth mirror has a wide range of uses. Three of its most important functions are allowing indirect vision by the dentist, reflecting light onto desired surfaces, and retraction of soft tissues. There exists 2 different norms of the thread that are not compatible to each other. The US norm have a taper thread and is mostly used in the United States, Canada, Spain and South Korea.[2] Indirect vision is needed in certain locations of the mouth where visibility is difficult or impossible. The posterior (or lingual) surfaces of the anterior maxillary teeth is a notable area where mouth mirrors are often used
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