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 has since been applied by analogy to topics outside 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. For instance, a single left–right spectrum of political opinion does not capture the full range of people's political beliefs. Political scientists use a variety of biaxial and multiaxial systems to more accurately characterize political opinion.
In most modern usages of spectrum there is a unifying theme between the extremes at either end. This was not always true in older usage.
In Latin, spectrum means "image" or "apparition", including the meaning "spectre". Spectral evidence is testimony about what was done by spectres of persons not present physically, or hearsay evidence about what ghosts or apparitions of Satan said. It was used to convict a number of persons of witchcraft at Salem, Massachusetts in the late 17th century. The word "spectrum" [Spektrum] was strictly used to designate a ghostly optical afterimage by Goethe in his Theory of Colors and Schopenhauer in On Vision and Colors.
In the 17th century, the word spectrum was introduced into optics by Isaac Newton, referring to the range of colors observed when white light was dispersed through a prism. Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot.
The term spectrum was expanded to apply to other waves, such as sound waves that could also be measured as a function of frequency, frequency spectrum and power spectrum of a signal. The term now applies to any signal that can be measured or decomposed along a continuous variable such as energy in electron spectroscopy or mass-to-charge ratio in mass spectrometry. Spectrum is also used to refer to a graphical representation of the signal as a function of the dependent variable.
Electromagnetic spectrum refers to the full range of all frequencies of electromagnetic radiation and also to the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. Devices used to measure an electromagnetic spectrum are called spectrograph or spectrometer. The visible spectrum is the part of the electromagnetic spectrum that can be seen by the human eye. The wavelength of visible light ranges from 390 to 700 nm. The absorption spectrum of a chemical element or chemical compound is the spectrum of frequencies or wavelengths of incident radiation that are absorbed by the compound due to electron transitions from a lower to a higher energy state. The emission spectrum refers to the spectrum of radiation emitted by the compound due to electron transitions from a higher to a lower energy state.
Light from many different sources contains various colors, each with its own brightness or intensity. A rainbow, or prism, sends these component colors in different directions, making them individually visible at different angles. A graph of the intensity plotted against the frequency (showing the brightness of each color) is the frequency spectrum of the light. When all the visible frequencies are present equally, the perceived color of the light is white, and the spectrum is a flat line. Therefore, flat-line spectra in general are often referred to as white, whether they represent light or another type of wave phenomenon (sound, for example, or vibration in a structure).
In radio and telecommunications, the frequency spectrum can be shared among many different broadcasters. The radio spectrum is the part of the electromagnetic spectrum corresponding to frequencies lower below 300 GHz, which corresponds to wavelengths longer than about 1 mm. The microwave spectrum corresponds to frequencies between 300 MHz (0.3 GHz) and 300 GHz and wavelengths between one meter and one millimeter. Each broadcast radio and TV station transmits a wave on an assigned frequency range, called a channel. When many broadcasters are present, the radio spectrum consists of the sum of all the individual channels, each carrying separate information, spread across a wide frequency spectrum. Any particular radio receiver will detect a single function of amplitude (voltage) vs. time. The radio then uses a tuned circuit or tuner to select a single channel or frequency band and demodulate or decode the information from that broadcaster. If we made a graph of the strength of each channel vs. the frequency of the tuner, it would be the frequency spectrum of the antenna signal.
In astronomical spectroscopy, the strength, shape, and position of absorption and emission lines, as well as the overall spectral energy distribution of the continuum, reveal many properties of astronomical objects. Stellar classification is the categorisation of stars based on their characteristic electromagnetic spectra. The spectral flux density is used to represent the spectrum of a light-source, such as a star.
In radiometry and colorimetry (or color science more generally), the spectral power distribution (SPD) of a light source is a measure of the power contributed by each frequency or color in a light source. The light spectrum is usually measured at points (often 31) along the visible spectrum, in wavelength space instead of frequency space, which makes it not strictly a spectral density. Some spectrophotometers can measure increments as fine as one to two nanometers. the values are used to calculate other specifications and then plotted to show the spectral attributes of the source. This can be helpful in analyzing the color characteristics of a particular source.
A plot of ion abundance as a function of mass-to-charge ratio is called a mass spectrum. It can be produced by a mass spectrometer instrument. The mass spectrum can be used to determine the quantity and mass of atoms and molecules. Tandem mass spectrometry is used to determine molecular structure.
In physics, the energy spectrum of a particle is the number of particles or intensity of a particle beam as a function of particle energy. Examples of techniques that produce an energy spectrum are alpha-particle spectroscopy, electron energy loss spectroscopy, and mass-analyzed ion-kinetic-energy spectrometry.
A source of sound can have many different frequencies mixed. A Musical tone's timbre is characterized by its harmonic spectrum. Sound in our environment that we refer to as noise includes many different frequencies. When a sound signal contains a mixture of all audible frequencies, distributed equally over the audio spectrum, it is called white noise.
The spectrum analyzer is an instrument which can be used to convert the sound wave of the musical note into a visual display of the constituent frequencies. This visual display is referred to as an acoustic spectrogram. Software based audio spectrum analyzers are available at low cost, providing easy access not only to industry professionals, but also to academics, students and the hobbyist. The acoustic spectrogram generated by the spectrum analyzer provides an acoustic signature of the musical note. In addition to revealing the fundamental frequency and its overtones, the spectrogram is also useful for analysis of the temporal attack, decay, sustain, and release of the musical note.
Antibiotic spectrum of activity is a component of antibiotic classification. A broad-spectrum antibiotic is active against a wide range of bacteria, whereas a narrow-spectrum antibiotic is effective against specific families of bacteria. An example of a commonly used broad-spectrum antibiotic is ampicillin. An example of a narrow spectrum antibiotic is Dicloxacillin, which acts on beta-lactamase-producing Gram-positive bacteria such as Staphylococcus aureus.
In psychiatry, the spectrum approach uses the term spectrum to describe a range of linked conditions, sometimes also extending to include singular symptoms and traits. For example, the autism spectrum describes a range of conditions classified as neurodevelopmental disorders.
In functional analysis, the concept of the spectrum of a bounded operator is a generalization of the eigenvalue concept for matrices.
In social science, economic spectrum is used to indicate the range of social class along some indicator of wealth or income. In political science, the term political spectrum refers to a system of classifying political positions in one or more dimensions, for example in a range including right wing and left wing.
5G (from "5th Generation") is the latest generation of cellular mobile communications. It succeeds the 4G (LTE-A, WiMax), 3G (UMTS, LTE) and 2G (GSM) systems. 5G performance targets high data rate, reduced latency, energy saving, cost reduction, higher system capacity, and massive device connectivity. The first phase of 5G specifications in Release-15 will be completed by April 2019 to accommodate the early commercial deployment. The second phase in Release-16 is due to be completed by April 2020 for submission to the International Telecommunication Union (ITU) as a candidate of IMT-2020 technology.The ITU IMT-2020 specification demands speeds of up to 20 Gbit/s, achievable with wide channel bandwidths and massive MIMO. 3rd Generation Partnership Project (3GPP) is going to submit 5G NR (New Radio) as its 5G communication standard proposal. 5G NR can include lower frequencies (FR1), below 6 GHz, and higher frequencies (FR2), above 24 GHz and into the millimeter waves range. However, the speed and latency in early deployments, using 5G NR software on 4G hardware (non-standalone), are only slightly better than new 4G systems, estimated at 15% to 50% better. Simulation of standalone eMBB deployments showed improved throughput between 2.5×, in the FR1 range, and nearly 20×, in the FR2 range.Asperger syndrome
Asperger syndrome (AS), also known as Asperger's, is a developmental disorder characterized by significant difficulties in social interaction and nonverbal communication, along with restricted and repetitive patterns of behavior and interests. As a milder autism spectrum disorder (ASD), it differs from other ASDs by relatively normal language and intelligence. Although not required for diagnosis, physical clumsiness and unusual use of language are common. Signs usually begin before two years of age and typically last for a person's entire life.The exact cause of Asperger's is unknown. While it is probably partly inherited, the underlying genetics have not been determined conclusively. Environmental factors are also believed to play a role. Brain imaging has not identified a common underlying problem. In 2013, the diagnosis of Asperger's was removed from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), and people with these symptoms are now included within the autism spectrum disorder along with autism and pervasive developmental disorder not otherwise specified (PDD-NOS). It remains within the International Classification of Diseases (ICD-11) as of 2019 but as a subtype of autism spectrum disorder.There is no single treatment, and the effectiveness of particular interventions is supported by only limited data. Treatment is aimed at improving poor communication skills, obsessive or repetitive routines and physical clumsiness. Interventions may include social skills training, cognitive behavioral therapy, physical therapy, speech therapy, parent training, and medications for associated problems, such as mood or anxiety. Most children improve as they grow up, but social and communication difficulties usually persist. Some researchers and people on the autism spectrum have advocated a shift in attitudes toward the view that autism spectrum disorder is a difference rather than a disease that must be treated or cured.In 2015, Asperger's was estimated to affect 37.2 million people globally. The syndrome is named after the Austrian pediatrician Hans Asperger, who, in 1944, described children in his practice who lacked nonverbal communication, had limited understanding of others' feelings, and were physically clumsy. The modern conception of Asperger syndrome came into existence in 1981 and went through a period of popularization. It became a standardized diagnosis in the early 1990s. Many questions and controversies remain. There is doubt about whether it is distinct from high-functioning autism (HFA). Partly because of this, the percentage of people affected is not firmly established.Autism
Autism is a developmental disorder characterized by difficulties with social interaction and communication and by restricted and repetitive behavior. Parents usually notice signs during the first three years of their child's life. These signs often develop gradually, though some children with autism reach their developmental milestones at a normal pace before worsening.Autism is associated with a combination of genetic and environmental factors. Risk factors during pregnancy include certain infections, such as rubella, toxins including valproic acid, alcohol, cocaine, pesticides and air pollution, fetal growth restriction, and autoimmune diseases. Controversies surround other proposed environmental causes; for example, the vaccine hypothesis, which has been disproven. Autism affects information processing in the brain by altering connections and organization of nerve cells and their synapses. How this occurs is not well understood. In the DSM-5, autism and less severe forms of the condition, including Asperger syndrome and pervasive developmental disorder not otherwise specified (PDD-NOS), have been combined into the diagnosis of autism spectrum disorder (ASD).Early speech therapy or behavioral interventions can help children with autism gain self-care, social, and communication skills. Although there is no known cure, there have been cases of children who recovered. Not many children with autism live independently after reaching adulthood, though some are successful. An autistic culture has developed, with some individuals seeking a cure and others believing autism should be accepted as a difference and not treated as a disorder.Globally, autism is estimated to affect 24.8 million people as of 2015. In the 2000s, the number of people affected was estimated at 1–2 per 1,000 people worldwide. In the developed countries, about 1.5% of children are diagnosed with ASD as of 2017, a more than doubling from 0.7% in 2000 in the United States. It occurs four-to-five times more often in males than females. The number of people diagnosed has increased dramatically since the 1960s, partly due to changes in diagnostic practice. The question of whether actual rates have increased is unresolved.Autism spectrum
Autism spectrum, also known as autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a range of neurodevelopmental disorders that includes autism, Asperger syndrome and other related conditions. Individuals on the spectrum are often hyper sensitive to sensory stimuli, and present with two types of symptoms: problems in social communication and social interaction; and restricted, repetitive patterns of behavior, interests or activities. Long term issues may include difficulties in performing daily tasks, creating and keeping relationships, and maintaining a job.Diagnosis is based on symptoms, which are typically recognized between one and two years of age. The DSM-5 redefined the autism spectrum disorders to encompass the previous diagnoses of autism, Asperger syndrome, pervasive developmental disorder not otherwise specified (PDD-NOS), and childhood disintegrative disorder.The cause of autism spectrum is uncertain, but risk factors include having an older parent, a family history of autism, and genetics. In 2018 it was discovered that somewhere between 74% and 93% of ASD risk is heritable.
The term "spectrum" can refer to both a range of both symptoms, and their severity, leading to some favoring a distinction between severely disabled autistics who cannot speak or look after themselves, and "higher functioning" autistics, such as Temple Grandin, listed in the 2010 Time 100 under the Heroes category as an autism spokesperson. However, many autistics who are able to communicate with allistics (non-autistic persons), including several prominent persons in the autism activism community and some parents, have rejected this system of "functioning labels", and the autism rights movement, encourages society to adopt a tolerance for neurodiversity by accepting spectrum autism as a variation in normal human functioning, rather than a "disorder" to be "cured".
Medical treatment efforts are generally individualized, and can include behavioural therapy, and the teaching of coping skills. Medications may be used to try to help improve symptoms, but there is little evidence to support their effectiveness. Higher functioning autistics can reduce their experience of symptoms by learning to adapt to what are uncomfortable or difficult environments for them, for instance by wearing headphones to alleviate hypersensitivity to noise.
Autism spectrum is estimated to affect about 1% of people (62.2 million globally as of 2015). Males are diagnosed more often than females.Bipolar disorder
Bipolar disorder, previously known as manic depression, is a mental disorder that causes periods of depression and periods of abnormally elevated mood. The elevated mood is significant and is known as mania or hypomania, depending on its severity, or whether symptoms of psychosis are present. During mania, an individual behaves or feels abnormally energetic, happy, or irritable. Individuals often make poorly thought out decisions with little regard to the consequences. The need for sleep is usually reduced during manic phases. During periods of depression, there may be crying, a negative outlook on life, and poor eye contact with others. The risk of suicide among those with the illness is high at greater than 6 percent over 20 years, while self-harm occurs in 30–40 percent. Other mental health issues such as anxiety disorders and substance use disorder are commonly associated with bipolar disorder.The causes are not clearly understood, but both environmental and genetic factors play a role. Many genes of small effect contribute to risk. Environmental risk factors include a history of childhood abuse and long-term stress. About 85% of the risk is attributed to genetics. The condition is classified as bipolar I disorder if there has been at least one manic episode, with or without depressive episodes, and as bipolar II disorder if there has been at least one hypomanic episode (but no manic episodes) and one major depressive episode. In those with less severe symptoms of a prolonged duration, the condition cyclothymic disorder may be diagnosed. If the symptoms are due to drugs or medical problems, it is classified separately. Other conditions that may present similarly include attention deficit hyperactivity disorder, personality disorders, schizophrenia and substance use disorder as well as a number of medical conditions. Medical testing is not required for a diagnosis, though blood tests or medical imaging can be done to rule out other problems.Treatment commonly includes psychotherapy as well as medications such as mood stabilizers and antipsychotics. Examples of mood stabilizers that are commonly used include lithium and various anticonvulsants. Involuntary treatment in a hospital may be needed if a person is a risk to themselves or others but refuses treatment. Severe behavioral problems, such as agitation or combativeness, may be managed with short term antipsychotics or benzodiazepines. In periods of mania, it is recommended that antidepressants be stopped. If antidepressants are used for periods of depression, they should be used with a mood stabilizer. Electroconvulsive therapy (ECT), while not very well studied, may be tried for those who do not respond to other treatments. If treatments are stopped, it is recommended that this be done slowly. Many individuals have financial, social or work-related problems due to the illness. These difficulties occur a quarter to a third of the time, on average. Due to lifestyle choices and the side effects of medications, the risk of death from natural causes such as heart disease in people with bipolar is twice that of the general population.Bipolar disorder affects approximately 1% of the global population. In the United States, about 3% are estimated to be affected at some point in their life; rates appear to be similar in females and males. The most common age at which symptoms begin is 25. The economic cost of the disorder has been estimated at $45 billion for the United States in 1991. A large proportion of this was related to a higher number of missed work days, estimated at 50 per year. People with bipolar disorder often face problems with social stigma.Charter Communications
Charter Communications, Inc. is an American telecommunications and mass media company that offers its services to consumers and businesses under the branding of Spectrum. Providing services to over 26 million customers in 41 states, it is the second-largest cable operator in the United States by subscribers, just behind Comcast, and third largest pay TV operator behind Comcast and AT&T. It is the fifth largest telephone provider based upon residential subscriber line count.
In late 2012, with the naming of longtime Cablevision executive Thomas Rutledge as their CEO, the company relocated its corporate headquarters from St. Louis, Missouri, to Stamford, Connecticut, although many operations still remain based out of St. Louis. On May 18, 2016, Charter completed its acquisition of Time Warner Cable and its sister company Bright House Networks, making it the third-largest pay television service in the United States. Charter ranked No. 74 in the 2018 Fortune 500 list of the largest United States corporations by total revenue.Electromagnetic spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length. Gamma rays, X-rays, and high ultraviolet are classified as ionizing radiation as their photons have enough energy to ionize atoms, causing chemical reactions. Exposure to these rays can be a health hazard, causing radiation sickness, DNA damage and cancer. Radiation of visible light wavelengths and lower are called nonionizing radiation as they cannot cause these effects.
In most of the frequency bands above, a technique called spectroscopy can be used to physically separate waves of different frequencies, producing a spectrum showing the constituent frequencies. Spectroscopy is used to study the interactions of electromagnetic waves with matter. Other technological uses are described under electromagnetic radiation.Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify the elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.Far-left politics
Far-left politics are political views located further on the left of the left-right spectrum than the standard political left.
The term has been used to describe ideologies such as: communism, anarchism, anarcho-communism, left-communism, anarcho-syndicalism, Marxism–Leninism, Trotskyism, and Maoism. Since 2016, the term Alt-left has also been used as a pejorative to refer to political views at the extreme end of this spectrum, and to those who adhere to such views.Fetal alcohol spectrum disorder
Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. Problems may include an abnormal appearance, short height, low body weight, small head size, poor coordination, low intelligence, behavior problems, and problems with hearing or seeing. Those affected are more likely to have trouble in school, legal problems, participate in high-risk behaviors, and have trouble with alcohol or other drugs. The most severe form of the condition is known as fetal alcohol syndrome (FAS). Other types include partial fetal alcohol syndrome (pFAS), alcohol-related neurodevelopmental disorder (ARND) and alcohol-related birth defects (ARBD). Some accept only FAS as a diagnosis, seeing the evidence as inconclusive with respect to other types.Fetal alcohol spectrum disorders are caused by drinking alcohol during pregnancy. Surveys from the United States have found about 10% of pregnant women have drunk alcohol in the last month, and 20% to 30% drank at some point during the pregnancy. About 4.7% of North American women who are pregnant are alcoholics. The risk of problems depends on the amount consumed and the frequency of consumption as well as when during pregnancy the alcohol is consumed. Other risk factors include an older mother, smoking, and poor diet. There is no known safe amount or safe time to drink during pregnancy. While drinking small amounts of alcohol does not cause abnormalities in the face, it may cause behavioral issues. Alcohol crosses the blood brain barrier and both directly and indirectly affects a developing baby. Diagnosis is based on signs and symptoms in the person.Fetal alcohol spectrum disorders are preventable by avoiding alcohol. For this reason, medical authorities recommend no alcohol during pregnancy or while trying to become pregnant. While the condition is permanent, treatment can improve outcomes. Interventions may include parent-child interaction therapy, efforts to modify child behavior, and possibly medications.FASD is estimated to affect between 2% and 5% of people in the United States and Western Europe. FAS is believed to occur in between 0.2 and 9 per 1000 live births in the United States. In South Africa, some populations have rates as high as 9%. The negative effects of alcohol during pregnancy have been described since ancient times. The lifetime cost per child with FAS was $2,000,000 in 2002 in the US. The term fetal alcohol syndrome was first used in 1973.Infrared
Infrared radiation (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye, although IR at wavelengths up to 1050 nanometers (nm)s from specially pulsed lasers can be seen by humans under certain conditions. IR wavelengths extend from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz), to 1 millimeter (300 GHz). Most of the thermal radiation emitted by objects near room temperature is infrared. As with all EMR, IR carries radiant energy and behaves both like a wave and like its quantum particle, the photon.
Infrared radiation was discovered in 1800 by astronomer Sir William Herschel, who discovered a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has a critical effect on Earth's climate.
Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements. It excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range.Infrared radiation is used in industrial, scientific, military,
law enforcement, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space such as molecular clouds, detect objects such as planets, and to view highly red-shifted objects from the early days of the universe. Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatus.
Extensive uses for military and civilian applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm (micrometers). Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, detection of grow-ops, remote temperature sensing, short-range wireless communication, spectroscopy, and weather forecasting.Left–right political spectrum
The left–right political spectrum is a system of classifying political positions, ideologies and parties, from equality on the left to social hierarchy on the right. Left-wing politics and right-wing politics are often presented as opposed, although a particular individual or group may take a left-wing stance on one matter and a right-wing stance on another; and some stances may overlap and be considered either left- or right-wing depending on the ideology. In France, where the terms originated, the Left has been called 'the party of movement' and the Right 'the party of order'. The intermediate stance is called centrism and a person with such a position is a moderate or centrist.Monica Rambeau
Monica Rambeau is a fictional character and superhero appearing in American comic books published by Marvel Comics. Initially known as Captain Marvel, the character joined and eventually became leader of the Avengers for a time. She later used the codenames Photon, Pulsar, and beginning in 2013, Spectrum.
Akira Akbar portrays a young Monica Rambeau as a child in the film Captain Marvel, which is set in the Marvel Cinematic Universe. This was the cinematic debut of the character.Political spectrum
A political spectrum is a system of classifying different political positions upon one or more geometric axes that represent independent political dimensions.
Most long-standing spectra include a left wing, which originally referred to seating arrangements in the French parliament after the Revolution (1789–1799). On a left–right spectrum, communism and socialism are usually regarded internationally as being on the left, Liberalism can mean different things in different contexts: sometimes on the left (social liberalism). Those with an intermediate outlook are sometimes classified as centrists. That said, liberals and neoliberals are often called centrists too. Politics that rejects the conventional left–right spectrum is often known as syncretic politics, though the label tends to mischaracterize positions that have a logical location on a two-axis spectrum because they seem randomly brought together on a one-axis left-right spectrum.
Political scientists have frequently noted that a single left–right axis is insufficient for describing the existing variation in political beliefs and often include other axes. Though the descriptive words at polar opposites may vary, often in popular biaxial spectra the axes are split between socio-cultural issues and economic issues, each scaling from some form of individualism (or government for the freedom of the individual) to some form of communitarianism (or government for the welfare of the community).Radio frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around twenty thousand times per second (20 kHz) to around three hundred billion times per second (300 GHz). This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range.Spectral density
The power spectrum of a time series describes the distribution of power into frequency components composing that signal. According to Fourier analysis, any physical signal can be decomposed into a number of discrete frequencies, or a spectrum of frequencies over a continuous range. The statistical average of a certain signal or sort of signal (including noise) as analyzed in terms of its frequency content, is called its spectrum.
When the energy of the signal is concentrated around a finite time interval, especially if its total energy is finite, one may compute the energy spectral density. More commonly used is the power spectral density (or simply power spectrum), which applies to signals existing over all time, or over a time period large enough (especially in relation to the duration of a measurement) that it could as well have been over an infinite time interval. The power spectral density (PSD) then refers to the spectral energy distribution that would be found per unit time, since the total energy of such a signal over all time would generally be infinite. Summation or integration of the spectral components yields the total power (for a physical process) or variance (in a statistical process), identical to what would be obtained by integrating over the time domain, as dictated by Parseval's theorem.
The spectrum of a physical process often contains essential information about the nature of . For instance, the pitch and timbre of a musical instrument are immediately determined from a spectral analysis. The color of a light source is determined by the spectrum of the electromagnetic wave's electric field as it fluctuates at an extremely high frequency. Obtaining a spectrum from time series such as these involves the Fourier transform, and generalizations based on Fourier analysis. In many cases the time domain is not specifically employed in practice, such as when a dispersive prism is used to obtain a spectrum of light in a spectrograph, or when a sound is perceived through its effect on the auditory receptors of the inner ear, each of which is sensitive to a particular frequency.
However this article concentrates on situations in which the time series is known (at least in a statistical sense) or directly measured (such as by a microphone sampled by a computer). The power spectrum is important in statistical signal processing and in the statistical study of stochastic processes, as well as in many other branches of physics and engineering. Typically the process is a function of time, but one can similarly discuss data in the spatial domain being decomposed in terms of spatial frequency.Spectrum (cable service)
Spectrum or Charter Spectrum is a trade name of Charter Communications, used to market consumer cable television, internet, telephone, and wireless services provided by the company.
The brand was first introduced in 2014; prior to that, these services were marketed primarily under the Charter name. Following the acquisitions of Time Warner Cable and Bright House Networks by Charter, these operations also assumed the Spectrum brand.Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 740 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 430–770 THz.
The spectrum does not contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations like magenta, for example, are absent because they can only be made from a mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors or spectral colors.
Visible wavelengths pass largely unattenuated through the Earth's atmosphere via the "optical window" region of the electromagnetic spectrum. An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue. The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum. The near infrared (NIR) window lies just out of the human vision, as well as the medium wavelength infrared (MWIR) window, and the long wavelength or far infrared (LWIR or FIR) window, although other animals may experience them.ZX Spectrum
The ZX Spectrum (UK: ) is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research.
Referred to during development as the ZX81 Colour and ZX82, it was launched as the ZX Spectrum by Sinclair to highlight the machine's colour display, compared with the black and white of its predecessor, the ZX81. The Spectrum was released as eight different models, ranging from the entry level with 16 KB RAM released in 1982 to the ZX Spectrum +3 with 128 KB RAM and built in floppy disk drive in 1987; together they sold over 5 million units worldwide (not counting clones).The Spectrum was among the first mainstream-audience home computers in the UK, similar in significance to the Commodore 64 in the US. The introduction of the ZX Spectrum led to a boom in companies producing software and hardware for the machine, the effects of which are still seen. Some credit it as the machine which launched the UK IT industry. Licensing deals and clones followed, and earned Clive Sinclair a knighthood for "services to British industry".The Commodore 64, Dragon 32, Oric-1, Oric Atmos, BBC Micro and later the Amstrad CPC range were rivals to the Spectrum in the UK market during the early 1980s. While the machine was officially discontinued in 1992, new software titles continue to be released – over 40 so far in 2018.