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Spectrum
A SPECTRUM (plural spectra or spectrums ) is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum . The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism . As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum . Spectrum
Spectrum
has since been applied by analogy to topics outside of optics. Thus, one might talk about the "spectrum of political opinion ", or the "spectrum of activity" of a drug, or the "autism spectrum ". In these uses, values within a spectrum may not be associated with precisely quantifiable numbers or definitions. Such uses imply a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion. Nonscientific uses of the term spectrum are sometimes misleading
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Intensity (physics)
In physics , INTENSITY is the power transferred per unit area , where the area is measured on the plane perpendicular to the direction of propagation of the energy. In the SI system, it has units watts per square metre (W/m2). It is used most frequently with waves (e.g. sound or light ), in which case the average power transfer over one period of the wave is used. Intensity can be applied to other circumstances where energy is transferred. For example, one could calculate the intensity of the kinetic energy carried by drops of water from a garden sprinkler . The word "intensity" as used here is not synonymous with "strength", "amplitude", "magnitude", or "level", as it sometimes is in colloquial speech. Intensity can be found by taking the energy density (energy per unit volume) at a point in space and multiplying it by the velocity at which the energy is moving. The resulting vector has the units of power divided by area (i.e., surface power density )
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Power (physics)
In physics, POWER is the rate of doing work . It is the amount of energy consumed per unit time. Having no direction, it is a scalar quantity. In the SI system , the unit of power is the joule per second (J/s), known as the watt in honour of James Watt
Watt
, the eighteenth-century developer of the steam engine . Another common and traditional measure is horsepower (comparing to the power of a horse). Being the rate of work, the equation for power can be written: P = W t {displaystyle P={frac {W}{t}}} The integral of power over time defines the work performed. Because this integral depends on the trajectory of the point of application of the force and torque, this calculation of work is said to be path dependent . As a physical concept, power requires both a change in the physical universe and a specified time in which the change occurs
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Frequency
FREQUENCY is the number of occurrences of a repeating event per unit of time . It is also referred to as TEMPORAL FREQUENCY, which emphasizes the contrast to spatial frequency and angular frequency . The PERIOD is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second (that is, 60 seconds divided by 120 beats ). Frequency
Frequency
is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio (sound ) signals, radio waves , and light
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Isaac Newton
SIR ISAAC NEWTON PRS (/ˈnjuːtən/ ; 25 December 1642 – 20 March 1726/27 ) was an English mathematician , astronomer , and physicist (described in his own day as a "natural philosopher ") who is widely recognised as one of the most influential scientists of all time and a key figure in the scientific revolution . His book Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations of classical mechanics . Newton also made seminal contributions to optics , and he shares credit with Gottfried Wilhelm Leibniz
Gottfried Wilhelm Leibniz
for developing the infinitesimal calculus . Newton's Principia formulated the laws of motion and universal gravitation that dominated scientists' view of the physical universe for the next three centuries
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Arthur Schopenhauer
ARTHUR SCHOPENHAUER (German: ; 22 February 1788 – 21 September 1860) was a German philosopher . He is best known for his 1818 work The World as Will and Representation (expanded in 1844), wherein he characterizes the phenomenal world as the product of a blind and insatiable metaphysical will . Proceeding from the transcendental idealism of Immanuel Kant
Immanuel Kant
, Schopenhauer developed an atheistic metaphysical and ethical system that has been described as an exemplary manifestation of philosophical pessimism , rejecting the contemporaneous post-Kantian philosophies of German idealism . Schopenhauer was among the first thinkers in Western philosophy to share and affirm significant tenets of Eastern philosophy (e.g., asceticism , the world-as-appearance ), having initially arrived at similar conclusions as the result of his own philosophical work
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Salem, Massachusetts
SALEM is a coastal city in Essex County , Massachusetts
Massachusetts
, in the United States
United States
, located on Massachusetts' North Shore . It is a New England bedrock of history and is considered one of the most significant seaports in Puritan
Puritan
American history. The city's reported population was 41,340 at the 2010 census. Salem and Lawrence are the county seats of Essex County, though the county government was abolished in 1999. The city is home to the House of Seven Gables , Salem State University , the Salem Willows
Salem Willows
Park, Forrest River Park, Federal Street District , Charter Street Historic District , and the Peabody Essex Museum
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Afterimage
An AFTERIMAGE is an image that continues to appear in one's vision after the exposure to the original image has ceased. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological (palinopsia ). Illusory palinopsia may be a pathological exaggeration of physiological afterimages. Afterimages occur because photochemical activity in the retina continues even when you are no longer experiencing the original stimulus. The remainder of this article refers to PHYSIOLOGICAL AFTERIMAGES. A common physiological afterimage is the dim area that seems to float before one's eyes after briefly looking into a light source, such as a camera flash. Afterimages are a common symptom of visual snow
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Wave
In physics , a WAVE is an oscillation accompanied by a transfer of energy . Frequency refers to the addition of time. Wave motion transfers energy from one point to another, which displace particles of the transmission medium–that is, with little or no associated mass transport. Waves consist, instead, of oscillations or vibrations (of a physical quantity), around almost fixed locations. A wave is a disturbance that transfers energy through matter or space. There are two main types of waves. Mechanical waves propagate through a medium, and the substance of this medium is deformed. Restoring forces then reverse the deformation. For example, sound waves propagate via air molecules colliding with their neighbors. When the molecules collide, they also bounce away from each other (a restoring force). This keeps the molecules from continuing to travel in the direction of the wave. The second main type, electromagnetic waves , do not require a medium
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Sound Wave
In physics , SOUND is a vibration that typically propagates as an audible wave of pressure , through a transmission medium such as air , water or other materials. In human physiology and psychology , sound is the reception of such waves and their perception by the brain . Humans can hear sound waves with frequencies between about 20 Hz and 20 kHz. Sound above 20 kHz is ultrasound and below 20 Hz is infrasound . Other animals have different hearing ranges
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Chemical Element
A CHEMICAL ELEMENT or ELEMENT is a species of atoms having the same number of protons in their atomic nuclei (i.e. the same atomic number , or Z). There are 118 elements that have been identified, of which the first 94 occur naturally on Earth
Earth
with the remaining 24 being synthetic elements . There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes , which decay over time into other elements. Iron
Iron
is the most abundant element (by mass ) making up Earth, while oxygen is the most common element in the Earth\'s crust . Chemical elements constitute all of the ordinary matter of the universe. However astronomical observations suggest that ordinary observable matter makes up only about 15% of the matter in the universe: the remainder is dark matter ; the composition of this is unknown, but it is not composed of chemical elements
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Chemical Compound
A CHEMICAL COMPOUND is a chemical substance composed of many identical molecules (or molecular entities ) composed of atoms from more than one element held together by chemical bonds . There are four types of compounds, depending on how the constituent atoms are held together: * molecules held together by covalent bonds * ionic compounds held together by ionic bonds * intermetallic compounds held together by metallic bonds * certain complexes held together by coordinate covalent bonds .Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service (CAS): its CAS number . A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using the standard abbreviations for the chemical elements, and subscripts to indicate the number of atoms involved
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1 E-7 M
The following are examples of orders of magnitude for different lengths . Objects of sizes in different order of magnitude
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Human Eye
The HUMAN EYE is an organ which reacts to light and pressure. As a sense organ , the mammalian eye allows vision . Human eyes help provide a three dimensional, moving image, normally coloured in daylight. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can differentiate between about 10 million colors and is possibly capable of detecting a single photon . Similar to the eyes of other mammals , the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock
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Electron Spectroscopy
ELECTRON SPECTROSCOPY is an analytical technique to study the electronic structure and its dynamics in atoms and molecules . In general an excitation source such as x-rays , electrons or synchrotron radiation will eject an electron from an inner-shell orbital of an atom. Detecting photoelectrons that are ejected by x-rays is called x-ray photoelectron spectroscopy (XPS) or electron spectroscopy for chemical analysis (ESCA). Detecting electrons that are ejected from higher orbitals to conserve energy during electron transitions is called Auger electron spectroscopy (AES). Experimental applications include high-resolution measurements on the intensity and angular distributions of emitted electrons as well as on the total and partial ion yields. Ejected electrons can escape only from a depth of approximately 3 nanometers or less, making electron spectroscopy most useful to study surfaces of solid materials
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Spectrograph
A SPECTROGRAPH is an instrument that separates light into a frequency spectrum and records the signal using a camera . There are several kinds of machines referred to as spectrographs, depending on the precise nature of the waves. The term was first used in July, 1876 by Dr. Henry Draper
Henry Draper
when he invented the earliest version of this device, and which he used to take several photographs of the spectrum of Vega . This earliest version of the spectrograph was cumbersome to use and difficult to manage. One way to define a spectrograph is as a device that separates light by its wavelength and records this data. A spectrograph typically has a multi-channel detector system or imaging system that detects the spectrum of light
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