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Modern Physics

Heisenberg Uncertainity Principle

Heisenberg’s Uncertainity principle: When we are studying a large moving objects say a planet, then we can follow its definite path on which it travels. If we know its initial position and momentum, then we can predict its position and momentum at any other time. But this is not possible for electron, proton and neutron which are microscopic particles. Heisenberg ...

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alpha beta and gamma radiation

Discovery of 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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What is quantization of energy

Quantization of energy: The assumptions made by Plank in deriving his radiation law and their consequences along with significance of Plank’s constant h were not immediately clear to his contemporaries and even to Plank himself.Plank derived his radiation law by analyzing the interaction between radiation in the cavity volume and the atoms of the cavity walls.He assumed that these atoms ...

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What is thermal radiation

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 lesser ...

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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

What is uncertainty principle? 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 predict its position ...

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Black body radiation

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 the energy is distributed ...

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The Photoelectric Effect experiment with animation

What is photoelectric effect? “When light of suitable frequency falls on a metal surface, electrons are emitted from the metal surface.This phenomenon is called photoelectric effect.” The electron emitted in this process are known as photoelectric. Explanation: Experimental Setup: The apparatus used to observe the photoelectric effect is shown in above Figure: It consists of an evacuated glass tube in ...

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