1.
Hydrogen spectral series
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The emission spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two levels in the atom. The classification of the series by the Rydberg formula was important in the development of quantum mechanics, the spectral series are important in astronomical spectroscopy for detecting the presence of hydrogen and calculating red shifts. A hydrogen atom consists of an electron orbiting its nucleus, the electromagnetic force between the electron and the nuclear proton leads to a set of quantum states for the electron, each with its own energy. These states were visualized by the Bohr model of the atom as being distinct orbits around the nucleus. Each energy state, or orbit, is designated by an integer, Spectral emission occurs when an electron transitions, or jumps, from a higher energy state to a lower energy state. To distinguish the two states, the energy state is commonly designated as n′, and the higher energy state is designated as n. The energy of a photon corresponds to the energy difference between the two states. Because the energy of state is fixed, the energy difference between them is fixed, and the transition will always produce a photon with the same energy. The spectral lines are grouped into series according to n′, lines are named sequentially starting from the longest wavelength/lowest frequency of the series, using Greek letters within each series. For example, the 2 →1 line is called Lyman-alpha, there are emission lines from hydrogen that fall outside of these series, such as the 21 cm line. These emission lines correspond to much rarer atomic events such as hyperfine transitions, the fine structure also results in single spectral lines appearing as two or more closely grouped thinner lines, due to relativistic corrections. Meaningful values are returned only when n is greater than n′, note that this equation is valid for all hydrogen-like species, i. e. atoms having only a single electron, and the particular case of hydrogen spectral lines are given by Z=1. The series is named after its discoverer, Theodore Lyman, who discovered the lines from 1906–1914. All the wavelengths in the Lyman series are in the ultraviolet band, named after Johann Balmer, who discovered the Balmer formula, an empirical equation to predict the Balmer series, in 1885. Balmer lines are referred to as H-alpha, H-beta, H-gamma and so on. Four of the Balmer lines are in the visible part of the spectrum, with wavelengths longer than 400 nm. Parts of the Balmer series can be seen in the solar spectrum, H-alpha is an important line used in astronomy to detect the presence of hydrogen
2.
H-alpha
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H-alpha is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm, it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alpha light is important to astronomers as it is emitted by many emission nebulae and can be used to observe features in the Suns atmosphere, according to the Bohr model of the atom, electrons exist in quantized energy levels surrounding the atoms nucleus. These energy levels are described by the quantum number n =1,2,3. Electrons may only exist in these states, and may only transit between these states, for the Lyman series the naming convention is, n =2 to n =1 is called Lyman-alpha, n =3 to n =1 is called Lyman-beta, etc. H-alpha has a wavelength of 656.281 nm, is visible in the red part of the electromagnetic spectrum, instead, after being ionized, the electron and proton recombine to form a new hydrogen atom. In the new atom, the electron may begin in any energy level, approximately half the time, this cascade will include the n =3 to n =2 transition and the atom will emit H-alpha light. Therefore, the H-alpha line occurs where hydrogen is being ionized, instead, molecules such as carbon dioxide, carbon monoxide, formaldehyde, ammonia, or acetonitrile are typically used to determine the mass of a cloud. A hydrogen-alpha filter is a filter designed to transmit a narrow bandwidth of light generally centred on the H-alpha wavelength. They are characterized by a width that measures the width of the wavelength band that is transmitted. These filters can be dichroic filters manufactured by multiple vacuum-deposited layers and these layers are selected to produce interference effects that filter out any wavelengths except at the requisite band. Taken in isolation, H-alpha dichroic filters are useful in astrophotography and they do not have narrow enough bandwidth for observing the suns atmosphere. This combination will pass only a range of wavelengths of light centred on the H-alpha emission line. The physics of the etalon and the dichroic interference filters are essentially the same, due to the high velocities sometimes associated with features visible in H-alpha light, solar H-alpha etalons can often be tuned to cope with the associated Doppler effect. Commercially available H-alpha filters for amateur solar observing usually state bandwidths in Angstrom units and are typically 0. 7Å, by using a second etalon, this can be reduced to 0. 5Å leading to improved contrast in details observed on the suns disc. An even more narrow band filter can be using a Lyot filter. Hydrogen spectral series Rydberg formula Spectrohelioscope Description of etalon filter by Colin Kaminski
3.
Visible spectrum
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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 light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm, in terms of frequency, this corresponds to a band in the vicinity of 430–770 THz. The spectrum does not, however, contain all the colors that the human eyes, unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass through the window, the region of the electromagnetic spectrum that allows wavelengths to pass largely unattenuated through the Earths atmosphere. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, the optical window is also referred to as the visible window because it overlaps the human visible response spectrum. The near infrared window lies just out of the vision, as well as the Medium Wavelength IR window. In the 13th century, Roger Bacon theorized that rainbows were produced by a process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light and he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. The result is red light is bent less sharply than violet as it passes through the prism. Newton divided the spectrum into seven named colors, red, orange, yellow, green, blue, indigo, the human eye is relatively insensitive to indigos frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right. However, the evidence indicates that what Newton meant by indigo, comparing Newtons observation of prismatic colors to a color image of the visible light spectrum shows that indigo corresponds to what is today called blue, whereas blue corresponds to cyan. In the 18th century, Goethe wrote about optical spectra in his Theory of Colours, Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow, the spectrum appears only when these edges are close enough to overlap. Young was the first to measure the wavelengths of different colors of light, the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century
4.
Naked eye
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Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered naked, in astronomy, the naked eye may be used to observe events that can be viewed without equipment, such as an astronomical conjunction, the passage of a comet, or a meteor shower. Sky lore and various tests demonstrate a wealth of phenomena that can be seen with the unaided eye. The basic accuracies of the eye are, Quick autofocus from distances of 25 cm to 50 cm to infinity. Angular resolution, about 1 arcminute, approximately 0. 02° or 0.0003 radians, field of view, simultaneous visual perception in an area of about 160° × 175°. Faint stars up to +8 magnitude under a dark sky. Photometry to ±10% or 1% of intensity – in a range between night and day of 1,10,000,000,000, symmetries of 10–20, see the measurements of Tycho Brahe and the Egyptians. Even a few hundred kilometers away from an area where the sky can appear to be very dark. For most people, these are likely to be the best observing conditions within their reach, under such typical dark sky conditions, the naked eye can see stars with an apparent magnitude up to +6m. Under perfect dark sky conditions where all light pollution is absent, the angular resolution of the naked eye is about 1′, however, some people have sharper vision than that. There is anecdotal evidence that people had seen the Galilean moons of Jupiter before telescopes were invented, Uranus, when discovered in 1781, was the first planet discovered using technology rather than being spotted by the naked eye. In practice, the extinction and dust reduces this number somewhat. In the center of a city, where the limiting magnitude due to extreme amounts of light pollution can be +4m or less. Colors can be seen but this is limited by the fact that the eye uses rods instead of cones to view fainter stars, the visibility of diffuse objects such as star clusters and galaxies is much more strongly affected by light pollution than is that of planets and stars. Under typical dark conditions only a few objects are visible. The Triangulum Galaxy is a difficult averted vision object and only visible at all if it is higher than 50° in the sky, the globular clusters M3 in Canes Venatici and M92 in Hercules are also visible with the naked eye under such conditions. Under really dark sky conditions, however, M33 is easy to see, many other Messier objects are also visible under such conditions. The most distant objects that have seen by the naked eye are nearby bright galaxies such as Centaurus A, Bodes Galaxy, Sculptor Galaxy
5.
Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
6.
Atomic physics
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Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and this comprises ions, neutral atoms and, unless otherwise stated, it can be assumed that the term atom includes ions. The term atomic physics can be associated with power and nuclear weapons, due to the synonymous use of atomic. Physicists distinguish between atomic physics — which deals with the atom as a system consisting of a nucleus and electrons — and nuclear physics, which considers atomic nuclei alone. As with many fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular. Physics research groups are usually so classified, Atomic physics primarily considers atoms in isolation. Atomic models will consist of a nucleus that may be surrounded by one or more bound electrons. It is not concerned with the formation of molecules, nor does it examine atoms in a state as condensed matter. It is concerned with such as ionization and excitation by photons or collisions with atomic particles. This means that the atoms can be treated as if each were in isolation. By this consideration atomic physics provides the underlying theory in physics and atmospheric physics. Electrons form notional shells around the nucleus and these are normally in a ground state but can be excited by the absorption of energy from light, magnetic fields, or interaction with a colliding particle. Electrons that populate a shell are said to be in a bound state, the energy necessary to remove an electron from its shell is called the binding energy. Any quantity of energy absorbed by the electron in excess of this amount is converted to kinetic energy according to the conservation of energy, the atom is said to have undergone the process of ionization. If the electron absorbs a quantity of less than the binding energy. After a certain time, the electron in a state will jump to a lower state. In a neutral atom, the system will emit a photon of the difference in energy, if an inner electron has absorbed more than the binding energy, then a more outer electron may undergo a transition to fill the inner orbital. The Auger effect allows one to multiply ionize an atom with a single photon, there are rather strict selection rules as to the electronic configurations that can be reached by excitation by light — however there are no such rules for excitation by collision processes
7.
Spectral line
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Spectral lines are often used to identify atoms and molecules from their characteristic spectral lines. Spectral lines are the result of interaction between a system and a single photon. When a photon has about the amount of energy to allow a change in the energy state of the system. A spectral line may be observed either as a line or an absorption line. Which type of line is observed depends on the type of material, an absorption line is produced when photons from a hot, broad spectrum source pass through a cold material. The intensity of light, over a frequency range, is reduced due to absorption by the material. By contrast, a bright, emission line is produced when photons from a hot material are detected in the presence of a spectrum from a cold source. The intensity of light, over a frequency range, is increased due to emission by the material. Spectral lines are highly atom-specific, and can be used to identify the composition of any medium capable of letting light pass through it. Several elements were discovered by means, such as helium, thallium. Mechanisms other than atom-photon interaction can produce spectral lines, depending on the exact physical interaction, the frequency of the involved photons will vary widely, and lines can be observed across the electromagnetic spectrum, from radio waves to gamma rays. In other cases the lines are designated according to the level of ionization by adding a Roman numeral to the designation of the chemical element, so that Ca+ also has the designation Ca II. Neutral atoms are denoted with the roman number I, singly ionized atoms with II, more detailed designations usually include the line wavelength and may include a multiplet number or band designation. Many spectral lines of hydrogen also have designations within their respective series. A spectral line extends over a range of frequencies, not a single frequency, in addition, its center may be shifted from its nominal central wavelength. There are several reasons for this broadening and shift and these reasons may be divided into two general categories – broadening due to local conditions and broadening due to extended conditions. Broadening due to conditions is due to effects which hold in a small region around the emitting element. Broadening due to extended conditions may result from changes to the distribution of the radiation as it traverses its path to the observer
8.
Hydrogen atom
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A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the mass of the universe. In everyday life on Earth, isolated hydrogen atoms are extremely rare, instead, hydrogen tends to combine with other atoms in compounds, or with itself to form ordinary hydrogen gas, H2. Atomic hydrogen and hydrogen atom in ordinary English use have overlapping, yet distinct, for example, a water molecule contains two hydrogen atoms, but does not contain atomic hydrogen. Attempts to develop an understanding of the hydrogen atom have been important to the history of quantum mechanics. The most abundant isotope, hydrogen-1, protium, or light hydrogen, contains no neutrons and is just a proton, protium is stable and makes up 99. 9885% of naturally occurring hydrogen by absolute number. Deuterium contains one neutron and one proton, deuterium is stable and makes up 0. 0115% of naturally occurring hydrogen and is used in industrial processes like nuclear reactors and Nuclear Magnetic Resonance. Tritium contains two neutrons and one proton and is not stable, decaying with a half-life of 12.32 years, because of the short half life, Tritium does not exist in nature except in trace amounts. Higher isotopes of hydrogen are only created in artificial accelerators and reactors and have half lives around the order of 10−22 seconds, the formulas below are valid for all three isotopes of hydrogen, but slightly different values of the Rydberg constant must be used for each hydrogen isotope. Hydrogen is not found without its electron in ordinary chemistry, as ionized hydrogen is highly chemically reactive. When ionized hydrogen is written as H+ as in the solvation of classical acids such as hydrochloric acid, in that case, the acid transfers the proton to H2O to form H3O+. Ionized hydrogen without its electron, or free protons, are common in the interstellar medium, experiments by Ernest Rutherford in 1909 showed the structure of the atom to be a dense, positive nucleus with a light, negative charge orbiting around it. This immediately caused problems on how such a system could be stable, classical electromagnetism had shown that any accelerating charge radiates energy described through the Larmor formula. If this were true, all atoms would instantly collapse, however seem to be stable. Furthermore, the spiral inward would release a smear of electromagnetic frequencies as the orbit got smaller, instead, atoms were observed to only emit discrete frequencies of radiation. The resolution would lie in the development of quantum mechanics, in 1913, Niels Bohr obtained the energy levels and spectral frequencies of the hydrogen atom after making a number of simple assumptions in order to correct the failed classical model. The assumptions included, Electrons can only be in certain, discrete circular orbits or stationary states, thereby having a set of possible radii
9.
Johann Jakob Balmer
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Johann Jakob Balmer was a Swiss mathematician and mathematical physicist. Balmer was born in Lausen, Switzerland, the son of a Chief Justice also named Johann Jakob Balmer and his mother was Elizabeth Rolle Balmer, and he was the oldest son. During his schooling he excelled in mathematics, and so decided to focus on that field when he attended university. He studied at the University of Karlsruhe and the University of Berlin, Johann then spent his entire life in Basel, where he taught at a school for girls. He also lectured at the University of Basel, in 1868 he married Christine Pauline Rinck at the age of 43. The couple had a total of six children, in his 1885 notice, he referred to h as the fundamental number of hydrogen. Balmer then used this formula to predict the wavelength for m =7, two of his colleagues, Hermann Wilhelm Vogel and William Huggins, were able to confirm the existence of other lines of the series in the spectrum of hydrogen in white stars. Balmers formula was found to be a special case of the Rydberg formula. 1 λ =4 h = R H with R H being the Rydberg constant for hydrogen, n 1 =2 for Balmers formula, and n 2 > n 1. A full explanation of why these formulas worked, however, had to wait until the presentation of the Bohr model of the atom by Niels Bohr in 1913, Balmer lines and Balmer series are named after him. The crater Balmer on the Moon is named after him, minor planet 12755 Balmer is named after him. OConnor, John J. Robertson, Edmund F. Johann Jakob Balmer, MacTutor History of Mathematics archive, University of St Andrews
