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Modern Physics

bohr atomic model and theory for hydrogen atom with postulates

 Bohr’s theory of the  hydrogen atom The Rutherford model of the atom and the experimental formula of atomic spectra helped Bohr is solving the problem of atomic structure.In 1913 he proposed a model for the structure of a hydrogen atom based on his experimental observations.  Bohr atomic model postulates Neil Bohr based his theory of hydrogen atom on the following ...

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Planck’s radiation law derivation

Rayleigh Jeans law and Wien’s formulae were failed to solve the problem of distribution of spectral radiancy among various wavelengths in cavity radiations because these formulas were based upon the classical theory. Planck’s quantum theory of radiation In 1900,Max Planck gave the new concept about the nature of radiation,called quantum theory of radiation in which planck assumed the discrete nature ...

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State the Pauli Exclusion Principle

According to Pauli Exclusion Principle no two electrons can have samples values of the quantum numbers n, l,ml and ms or they can not have all these quantum numbers similar; at least one of the four numbers which are strictly required to Specify the state of an electron should be different from the quantum numbers which specify the state of an other electron ...

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Special and general theory of relativity

Theory of Relativity The theory of relativity is concerned with the way in which the observers who are in a state of relative motion describe the physical phenomenon. Theory of relativity is given by Albert Einstein in 1905 which states that there is no absolute state exist in the universe, all states are relative. The theory of relativity is concerned ...

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Properties and applications of laser light

Properties of laser light Laser light is highly monochromatic Tungsten light spread over a continuous spectrum, gives no basis for comparison. The light from selected lines in a gas discharge tube (line spectrum) however can have wavelengths in the visible region that are precise to about 1 part in 106. The sharpness of definition of laser light can easily be ...

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types of elementary particles

How many types of elementary particles are there? An elementary particle is a simple particle which is not a combination of other particles. For example, an electron is an elementary particle. There are 30 elementary particles out of which the following 7 elementary particles are stable out the nucleus. List of elementary particles Electron Proton Neutron Photon Neutrino Antineutrino Positron ...

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Binding Energy and mass defect

Physically, we define the binding energy as the positive work necessary to dissemble a nucleus into its constituents (nucleons). Equivalently  it is the energy liberated when Z proton and N neutrons combine to form a nucleus. For visualization, consider the simplest example of the deutron disintegration. The deutron atom H12 has a mass of 1.014102 a.m.u while the mass of the hydrogen ...

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Cosmic rays : Definition,uses and effects

The rays which receive on earth from outer space are called cosmic rays.It has been found that extremely penetrating radiations consisting of charged and uncharged particles and photons are reaching the earth. These radiations are called Cosmic Radiations. The sources of these radiations lie beyond the sun or the other stars of our galaxy. The radiations reaching the top of ...

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Difference and relationship between stress and strain

Stress It is defined as the force applied on unit area to produce change in the shape,volume or length of a body.Mathematically it is expressed as: The SI unit of stress (σ) is newton per square meter (Nm-2),which is given the name pascal  (pa). Stress may cause a change in length,volume and shape. Tensile stress When a stress  changes the ...

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Difference between young’s modulus,bulk modulus and shear modulus

Young’s modulus The ratio of tensile stress to tensile  strain is called young’s modulus. Young’s modulus formula Bulk modulus For three dimensional deformation,when volume is involved,then the ratio of applied stress to volumetric strain is called Bulk modulus.Mathematically it is expressed as: Bulk modulus formula Where ΔV is the change in original volume V. Shear modulus The ratio of shear stress ...

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