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ch27_part2 - Chapter 27 part 2 PHY213 X-Rays Production of...

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Chapter 27, part 2 PHY213 1 X-Rays Electromagnetic radiation with short wavelengths Wavelengths less than for ultraviolet Wavelengths are typically about 0.1 nm X-rays have the ability to penetrate most materials with relative ease Discovered and named by Roentgen in 1895 Production of X-rays, 1 X-rays are produced when high-speed electrons are suddenly slowed down Can be caused by the electron striking a metal target A current in the filament causes electrons to be emitted These freed electrons are accelerated toward a dense metal target The target is held at a higher potential than the filament X-ray Spectrum The x-ray spectrum has two distinct components Continuous broad spectrum Depends on voltage applied to the tube Sometimes called bremsstrahlung The sharp, intense lines are called characteristic X-rays, because they depend on the nature of the target material Production of X-rays, 2 An electron passes near a target nucleus The electron is deflected from its path by its attraction to the nucleus This produces an acceleration It will emit electromagnetic radiation when it is accelerated
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Chapter 27, part 2 PHY213 2 Wavelengths Produced If the electron loses all of its energy in the collision, the initial energy of the electron is completely transformed into a photon, i.e.-K ei =e V , K ef =0 The wavelength can be found from | K e,max | = max min ƒ hc e V h Wavelengths Produced, cont Not all radiation produced is at this wavelength Many electrons undergo more than one collision before being stopped This results in the continuous spectrum produced Diffraction of X-rays by Crystals (will not be tested) For diffraction to occur, the spacing between the lines must be approximately equal to the wavelength of the radiation to be measured The regular array of atoms in a crystal
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ch27_part2 - Chapter 27 part 2 PHY213 X-Rays Production of...

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