JEE Main & Advanced Sample Paper JEE Main Sample Paper-43

  • question_answer
    When the voltage applied to an X-rays tube increases from \[{{V}_{1}}=10kV\]to \[{{V}_{2}}=20\,kV\], the wavelength interval between \[{{K}_{\alpha }}\] line and cut-off wavelength of continuous spectrum increases by a factor of 3. Atomic number of the metallic target is

    A)  28                              

    B)  29              

    C)  65                              

    D)  66

    Correct Answer: B

    Solution :

     The cut-off wavelength when \[\Rightarrow \] is, \[\lambda =\frac{20}{2n+1},\,\,n=0,\,\,1,\,\,2,...\]            ?(i) The cut-off wavelength when \[\Rightarrow \] is \[\lambda =20,\,\frac{20}{3},\,\frac{20}{5},\,\frac{20}{7},...\]            ?(ii) The wavelength corresponding to \[\phi \] line is. \[\tan \,\phi =\frac{V}{H}\]                ?(iii) From given information, \[\theta \] Solving above equation, we get \[H'=H\,\cos \,\theta ,\].with the help of Eqs. (i), (ii) and (iii).

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