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Stopping potential of 24, 100, 110 and 115 k V are measured for photoelectrons emitted from a certain element when it is radiated with monochromatic X-ray . If this element is used as a target in an X-ray tube,what will be the wavelength of `K_a` - line? |
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Answer» Correct Answer - A::C Stopping potentials are 24, 100, 110 and 115 kV, i.e. if the electrons are emitted from conduction band maximum kinetic energy of photoelectrons would be `115xx10^3` eV. If they are emitted from next inner shell, maximum kinetic energy of photoelectrons would be `110xx10^3 eV` and so on. for photoelectrons of L- shell it would be `100xx10^3` eV and for K- shell it is`24xx10^3` ev. Therefore, diference between energy of L-shell and K-shell is `Delta E = E_L - K_K` `=(100 - 24)xx10^3 eV` `= 76xx10^3`eV `:.` Wavelength of `K_a` line (transition of electron form L-shell to K-shell) is, `lambda_(ka) (in Å) = (12375)/(DeltaE(in eV) = (12375)/(76xx10^3)` `= 0.163 Å`. |
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