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Modern Physics

Does a photon have a de Broglie wavelength?

Yes a photon has de Broglie wavelength.In 1924,Louis de Broglie proposed that a particle must also act like wave,in silmilar way,wave behave like particles. In de Broglie hypothesis an electromagnetic wave is the de-Broglie wave for a photon moving with speed c.According to de-Broglie ,the wavelength of the photon is given by the relation: λ = h/p Where P is ...

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Properties and applications of x rays

What are X rays ? X-rays are the electromagnetic waves which are emitted by the atoms of those metals which have large atomic number,large number of protons in their nuclei so that the pull of the nuclei on their electrons is very large.When an electron of K or L shell of such an atom is displaced from these shells to ...

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Properties and uses of alpha,beta and gamma rays

What is radioactivity? In the March 1896 Henri Becquerel announced the discovery of radioactivity similar to X-rays.Although rays (X-rays) had been discovered less than four month earlier it was already known that X-rays come from the fluorescence wall of the discharge tube and thus it was thought that fluorescence and phosphorescence might be responsible for them. Becquerel known that Uranium ...

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Thermal radiation:Definition,examples and properties

Thermal radiation Radiation emitted by such a body due to its temperature is called thermal radiation.All bodies not only emit such radiation but also absorb it from their surroundings.If the rate of absorption and emission from a body become equal ,the body is said to be in thermal equilibrium with its surroundings. The spectrum of thermal radiation from a hot ...

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What is Photovoltaic effect

Photovoltaic effect: An effect arising when a junction exists between two dissimilar materials and one of the materials is exposed to electromagnetic radiation,usually in the range near ultraviolet to infrared.The two materials may,for example,be a metal and a semiconductor or two semiconductors of opposite polarity,the combination forming a Schottky barrier and a P-N junction respectively.A forward voltage appears across the ...

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What instrument is used to measure atmospheric pressure?

  Barometer is an instrument used to measure atmospheric pressure. How can we measure atmospheric pressure by mercury barometer? Mercury barometers consist of a glass tube about 80 cm long,closed at one end.The tube is filled with mercury and then placed,open end downward,in a reservoir of mercury.As the atmospheric pressure changes ,the level of the mercury changes and to a ...

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bohr model for hydrogen

 Bohr’s theory of the  hydrogen atom: The Rutherford model of 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’s postulates: Neil Bohr based his theory of hydrogen atom on the following three postulates. 1:The ...

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Heisenberg uncertainty principle proof

What is the  uncertainty principle of Heisenberg? Uncertainty principle is defined as:”It is impossible to measure simultaneously both the position and momentum of a microscopic particle with accuracy or certainty.” When we are studying a large moving object say a planet,then we can follow its definition path on which it travels.If we know its initial position and momentum,then we can ...

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Black body radiation and planck’s radiation law

Black body radiation basics When a body is heated,it emits radiation.The nature of the radiation depends upon the temperature.At low temperature,a body emits radiation which is principally of long wavelengths in the invisible infrared region.At high temperature ,the proportion of shorter wavelength radiation increases. Furthermore,the amount of emitted radiation is different for different wavelengths.It is of interest to see how ...

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What is laser? how does it works?

What is laser? The name “LASER” stands for light Amplification by Stimulated Emission of Radiation.The lasers are used to produce light having following properties: Monochromatic Directionality Brightness Coherence Polarization One of the most important property of laser light is its monochromaticity. The word monochromatic comes from Greek word monos means single and chroma means colour. actually all lasers have very ...

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