BHU PMT BHU PMT Solved Paper-2002

  • question_answer
    The energy diffuse between the first two levels of hydrogen atom is\[{{10}^{2}}\,\,\pi J\]. For another element of atomic number 10 and mass number 20, this will be :                                                   [BHU PMT-2002]

    A)                  \[{{10}^{3}}\,\,\pi J\]                                    

    B)                  \[V={{I}_{b}}{{R}_{b}}\]

    C)                  \[\Rightarrow \]                                             

    D)                  \[{{R}_{b}}=\frac{V}{{{I}_{b}}}\]

    Correct Answer: D

    Solution :

                     The energy expression in terms, of Rydberg?s, Planck?s constant \[h\] and velocity of light \[c\] is                                 \[E=-{{Z}^{2}}\frac{Rhc}{{{n}^{2}}}\]                 Where \[Z\] is atomic number. The expression on keeping the values of constants, reduces to                 \[E=-{{Z}^{2}}\frac{13.6}{{{n}^{2}}}eV\]                 Where \[Z=1\] \[\left( hydrogen \right)\], \[{{n}_{1}}=1,\,\,{{n}_{2}}=2\], we have \[{{E}_{1}}=-{{\left( 1 \right)}^{2}}\times 13.6\left( \frac{1}{{{1}^{2}}}-\frac{1}{{{2}^{2}}} \right)\]                                 \[=-13.6\left( 1-\frac{1}{4} \right)\]                         ?.(1)                 When \[Z=10,\,\,{{n}_{1}}=1,\,{{n}_{2}}=2\], we have                                 \[{{E}_{2}}=-{{\left( 10 \right)}^{2}}\times 13.6\left( \frac{1}{1}-\frac{1}{{{2}^{2}}} \right)\]           ?(2)                 Dividing \[Eq.\,\left( 1 \right)\,\,by\,\,Eq.\,\,\left( 2 \right),\,we\,get\]                                                 \[\frac{{{E}_{1}}}{{{E}_{2}}}=\frac{1}{100}\]                 \[\Rightarrow \]                               \[{{E}_{2}}=100\times {{E}_{1}}\]                 Given,                   \[{{E}_{1}}=10.2\,\,eV\]                 \[\therefore \]                  \[{{E}_{2}}=100\times 10.2=1020\,\,eV\]


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