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Bohr model

In atomic physics, the Rutherford–Bohr model or Bohr model, presented by Niels Bohr and Ernest Rutherford in 1913, is a system consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar System, but with attraction provided by electrostatic forces in place of gravity. After the cubic model, the plum-pudding model, the Saturnian model, the Rutherford model came the Rutherford–Bohr model or just Bohr model for short; the improvement to the Rutherford model is a quantum physical interpretation of it. The model's key success lay in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen. While the Rydberg formula had been known experimentally, it did not gain a theoretical underpinning until the Bohr model was introduced. Not only did the Bohr model explain the reasons for the structure of the Rydberg formula, it provided a justification for the fundamental physical constants that make up the formula's empirical results; the Bohr model is a primitive model of the hydrogen atom, compared to the valence shell atom model.

As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader and much more accurate quantum mechanics and thus may be considered to be an obsolete scientific theory. However, because of its simplicity, its correct results for selected systems, the Bohr model is still taught to introduce students to quantum mechanics or energy level diagrams before moving on to the more accurate, but more complex, valence shell atom. A related model was proposed by Arthur Erich Haas in 1910 but was rejected; the quantum theory of the period between Planck's discovery of the quantum and the advent of a mature quantum mechanics is referred to as the old quantum theory. In the early 20th century, experiments by Ernest Rutherford established that atoms consisted of a diffuse cloud of negatively charged electrons surrounding a small, positively charged nucleus. Given this experimental data, Rutherford considered a planetary model of the atom, the Rutherford model of 1911 – electrons orbiting a solar nucleus – however, the said planetary model of the atom has a technical difficulty: the laws of classical mechanics predict that the electron will release electromagnetic radiation while orbiting a nucleus.

Because the electron would lose energy, it would spiral inwards, collapsing into the nucleus on a timescale of around 16 picoseconds. This atom model is disastrous; as the electron spirals inward, the emission would increase in frequency as the orbit got smaller and faster. This would produce a continuous smear, in frequency, of electromagnetic radiation. However, late 19th century experiments with electric discharges have shown that atoms will only emit light at certain discrete frequencies. To overcome this hard difficulty, Niels Bohr proposed, in 1913, what is now called the Bohr model of the atom, he put forward these three postulates that sum up most of the model: The electron is able to revolve in certain stable orbits around the nucleus without radiating any energy, contrary to what classical electromagnetism suggests. These stable orbits are called stationary orbits and are attained at certain discrete distances from the nucleus; the electron cannot have any other orbit in between the discrete ones.

The stationary orbits are attained at distances for which the angular momentum of the revolving electron is an integral multiple of the reduced Planck's constant: m e v r = n ℏ, where n = 1, 2, 3... is called the principal quantum number, ħ = h/2π. The lowest value of n is 1. Once an electron is in this lowest orbit, it can get no closer to the proton. Starting from the angular momentum quantum rule, Bohr was able to calculate the energies of the allowed orbits of the hydrogen atom and other hydrogen-like atoms and ions; these orbits are associated with definite energies and are called energy shells or energy levels. In these orbits, the electron's acceleration does not result in energy loss; the Bohr model of an atom was based upon Planck's quantum theory of radiation. Electrons can only gain and lose energy by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation with a frequency ν determined by the energy difference of the levels according to the Planck relation: Δ E = E 2 − E 1 = h ν, where h is Planck's constant.

Other points are: Like Einstein's theory of the photoelectric effect, Bohr's formula assumes that during a quantum jump a discrete amount of energy is radiated. However, unlike Einstein, Bohr stuck to the classical Maxwell theory of the electromagnetic field. Quantization of the electromagnetic field was explained by the discreteness of the atomic energy levels. According to the Maxwell theory the frequency ν of classical radiation is equal to the rotation frequency νrot of the electron in its orbit, with harmonics at integer multiples of this frequency; this result is obtained from the Bohr model for jumps between energy levels En and En−k when k is much smaller than n. These jumps reproduce the frequency of the k-th harmonic of orbit n. For sufficiently large values of n, the two orbits involved in the emission

Murshidabad (Vidhan Sabha constituency)

Murshidabad is an assembly constituency in Murshidabad district in the Indian state of West Bengal. As per orders of the Delimitation Commission, No. 64 Murshidabad covers Murshidabad municipality, Jiaganj Azimganj municipality and Murshidabad Jiaganj community development blockMurshidabad is part of No. 11 Murshidabad. In the 2011 election, Shaoni Singha Roy of Congress defeated her nearest rival Bibhas Chakraborty of Forward Bloc..# Congress did not contest the seat in 2006. Note: New constituencies – 4, constituencies abolished – 1 In the 2006 state assembly elections, Bivas Chakraborty of Forward Bloc won the Murshidabad assembly seat defeating his nearest rival Joyanta Roy of IPFB. Contests in most years were multi cornered but only winners and runners are being mentioned. Chhaya Ghosh of Forward Bloc defeated Abdul Mannan Hossain, Independent, in 2001. Mazammel Haque, defeated Abdul Ohab Mondal of Congress in 1996, Chhaya Ghosh of Forward Bloc defeated Asak Ali of Congress in 1991. Abdul Mannan Hossain of Congress defeated Madan Mohan Ray, Independent, in 1987.

Chhaya Ghosh of Forward Bloc defeated Dedar Bakshi of ICS in 1982 and Syed Nawab Jani Meerza of Janata Party in 1977. Mohammad Idris Ali of Congress won in 1972, 1971 and 1969. S. K. A. Mirza of Congress won in 1967. Birendra Narayan Ray, won in 1962. Durgapada Sinha of Congress won in 1957 and in independent India's first election in 1951

Welcome Back, Brotter

Welcome Back, Brotter is a television series broadcast on butv10 on Boston University's campus. The show follows the misadventures of two loser college roommates on the quest for popularity in their big city school. Welcome Back, Brotter won a College Emmy in 2013, it received a Telly Award in 2012. The 33rd Annual Telly Awards honored the Golden Age of Television-themed episode "Allston All-Nighter."The show won the following year in the 34th Annual Telly Awards, taking home the prize for the science fiction-themed episode "Back To The Brotter." The series is the first in the network's history to win two Telly Awards in two consecutive years. 11Creative Productions, which produces the show won the Grand Prize in Boston University's "Your Take" Short Film Festival in 2009. Each episode parodies a different narrative style; such formats have included mockumentary filmmaking, action parodies, in-studio informercials, voice-over narration, laugh tracks. There is a cold open; the theme song, "Oh, Brotter," which plays the opening and closing credits, is written and performed by Brian Engles.

Welcome Back, Brotter is produced by 11C Productions. The company's name derives from the place where the producers met: 11C, the College of Communication floor of Warren Towers' Shields Tower. In 2009, when 11C Productions was founded, the production company started producing Welcome Back as a webseries. Ryan came up with the idea for the pilot after recognizing that Brotter's last name rhymed with the popular show Welcome Back, Kotter; the first webisode was co-written and edited by John Sanderson. In 2011, the three became Executive Producers when buTV10 picked up the webseries as a televised production. Equipped with more than 20 Production Assistants, the show airs on-campus on Channel 10, which reaches nearly 30,000 students and 10,000 faculty members. All episodes and satirical promos are available and free online; the television debut of Welcome Back, Brotter was the subject of an article in BU Today by New York Times Magazine writer Susan Segilson. Bostonia magazine selected the feature as one of their Web Exclusives.

Welcome Back, Brotter was the subject of articles in The Daily Free Press in 2009, The Quad in 2010, Boston.com in 2013. WBB on IMDB WBB Official Website WBB on YouTube WBB on Twitter WBB on Facebook