NEET AIPMT SOLVED PAPER SCREENING 2005

  • question_answer
                    The ratio of the dimensions of Planck's constant and that of the moment of inertia is the dimension of:

    A)                                                                                                                                                                                                            frequency          

    B)                 velocity

    C)                 angular momentum

    D)                 rime

    Correct Answer: A

    Solution :

                    E = hv                         \[\Rightarrow h=\text{Planck }\!\!'\!\!\text{ s}\,\text{constant}\,\,\text{=}\frac{\text{E}}{\text{v}}\]                 \[\therefore [h]=\frac{[E]}{[v]}=\frac{[M{{L}^{2}}{{T}^{-2}}]}{[{{T}^{-1}}]}\]                 \[=[M{{L}^{2}}{{T}^{-1}}]\]                 and I = moment of inertia = MR2                 \[\Rightarrow \,\,\,\,[I]=[M]\,[{{L}^{2}}]\,\,=[M{{L}^{2}}]\]                 Hence,  \[\frac{[h]}{[I]}=\frac{[M{{L}^{2}}{{T}^{-1}}]}{[M{{L}^{2}}]}=[{{T}^{-1}}]\]                 \[=\frac{1}{[T]}=\dimension\,of\,frequency\]                 Alternative: \[\frac{h}{I}=\frac{E/v}{I}\]                 \[=\frac{E\times T}{I}=\frac{(kg\,{{m}^{2}}/{{s}^{2}})\times s}{(kg\,{{m}^{2}})}\]                 \[=\frac{1}{s}=\frac{1}{time}=\text{frequency}\]                 Thus, dimensions of \[\frac{h}{I}\] is same of frequency.


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