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Electrons each having the energy 80 keV are incident on the tungsten target of an X-ray tube. K-shell electrons of tungsten have –72.5 keV energy. The X-rays emitted by the tube contain only (a) a continuous X-ray spectrum (bremsstrahlung) with a minimum wavelength of ~0.0155 nm (b) a continuous X-ray spectrum (bremsstrahlung) with all wavelengths (c) the characteristic X-ray spectrum of tungsten (d) a continuous X-ray spectrum (bremsstrahlung) with a minimum wavelength of ~0.0155 nm and the characteristic X-ray spectrum of tungsten |
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Answer» Correct Answer is: (d) a continuous X-ray spectrum (bremsstrahlung) with a minimum wavelength of ~0.0155 nm and the characteristic X-ray spectrum of tungsten As the energy of the incident electrons is greater than the magnitude of the energy of the K-shell electrons, the target atoms will have vacancies in the K shell (K-shell electrons will be knocked out). This will cause emission of the entire characteristic spectrum of tungsten. Along with this, continuous X-rays will always be present, with λc = 1242 nm eV / 80 x 103 eV ≅ 0.0155 nm. |
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