RAJASTHAN PMT Rajasthan - PMT Solved Paper-2004

  • question_answer
    The radius of first Bohr orbit is \[0.5\,\overset{\text{o}}{\mathop{\text{A}}}\,,\] then radius of fourth Bohr orbit will be:

    A)  \[0.03\,\overset{\text{o}}{\mathop{\text{A}}}\,\]                         

    B)  \[0.12\,\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C)  \[2.0\,\overset{\text{o}}{\mathop{\text{A}}}\,\]           

    D)         \[8.0\,\overset{\text{o}}{\mathop{\text{A}}}\,\]

    Correct Answer: D

    Solution :

    The radius of Bohr or bit, \[r\propto {{n}^{2}}\] \[\therefore \]  \[\frac{{{r}_{1}}}{{{r}_{2}}}={{\left( \frac{{{n}_{1}}}{{{n}_{2}}} \right)}^{2}}\] \[\Rightarrow \]               \[{{r}_{2}}={{r}_{1}}{{\left( \frac{{{n}_{2}}}{{{n}_{1}}} \right)}^{2}}\]                        ?(1) Given:\[{{r}_{1}}=0.5\,\overset{{}^\circ }{\mathop{\text{A}}}\,\],\[{{n}_{1}}=1,{{n}_{2}}=4\] Putting given values in eq. (1) \[\therefore \]  \[{{r}_{2}}=0.5{{\left( \frac{4}{1} \right)}^{2}}\] \[\Rightarrow \]               \[{{r}_{2}}=0.5\times 16\] \[\therefore \]  \[{{r}_{2}}=8\,\overset{{}^\circ }{\mathop{\text{A}}}\,\]


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