《生产安全事故应急条例》（国务院令第708号）是一部（）。

A photon having 40 keV scatters from a free electron at rest.What is the maximum energy that the electron can obtain？（）

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A photon of wavelength 2.0 nm Compton-scatters from an electron at an angle of 90°.What is the modified wavelength？（）

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The momentum of photons corresponding to the minimum wavelength emitted from x-ray tube whose operating voltage is 120 kV is（）

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An X-ray tube operates at 100 kV.The maximum speed of electrons striking the anticathode is（）

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If the K， L， and M energy levels of Pt are 78000 eV， 12000 eV and 30000 eV， respectively， the wavelength of Ka line from Pt is（）

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When the atomic number of the anticathode is 79， the frequency of Ka line is（）

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In Zn the ionization energy of K shell is 9.659 KeV and L shell 1.021 KeV.The kinetic energy of the Auger electron emitted from the L shell is（）

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Liquid helium（atomic weight 4.003） has a density r= 0.13 g/cm3.Estimate the radius of a He atom， assuming that the atoms are packed in the densest possible configuration， which fills 74% of the space.（）。

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Through what angle is a 4 MeV a particle scattered when it approaches a gold nucleus with a impact parameter of 2.6 X 10-13 m？（）。

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The energy of a hydrogen atom in the first excited state is（）

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