Haryana PMT Haryana PMT Solved Paper-2001

  • question_answer
    An X-ray tube is operated on 30 kV. What is   the minimum wavelength emitted\[(h=6.6\times {{10}^{-34}})\,\text{Js,}\,\text{c=3}\times \text{1}{{\text{0}}^{8}}\,m/s,\]\[e=1.6\times {{10}^{-19}}C):\]

    A) \[6.6\overset{\text{o}}{\mathop{\text{A}}}\,\]

    B) \[1.2\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C) \[0.133\overset{\text{o}}{\mathop{\text{A}}}\,\]

    D) \[0.41\overset{\text{o}}{\mathop{\text{A}}}\,\]

    Correct Answer: D

    Solution :

                    Using the relation, \[\lambda =\frac{12375}{eV}{{\overset{\text{o}}{\mathop{\text{A}}}\,}_{unit}}\] Given,    \[V=30\text{ }kV\text{ }=30000\]                 \[\lambda =\frac{12375}{30000}=0.41\overset{\text{o}}{\mathop{\text{A}}}\,\] For hydrogen atom                                       \[\frac{1}{\lambda }=R\left( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right)\] According to de Broglie                 \[p=\frac{h}{\lambda }\] Momentum   \[p=hR\left( \frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}} \right)\] \[p=6.6\times {{10}^{-34}}\times 1.0974\times {{10}^{7}}\left( \frac{1}{{{1}^{2}}}-\frac{1}{{{4}^{2}}} \right)\] \[p=6.8\times {{10}^{-27}}Nm\]


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