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JEE Main & Advanced JEE Main Paper (Held On 10 April 2015)

  • question_answer
    de-Broglie wavelength of an electron accelerated by a voltage of 50 V is close to \[(|e|=1.6\times {{10}^{-19}}C,{{m}_{e}}=9.1\times {{10}^{-31}}kg,h=6.6\times {{10}^{-34}}Js)\] JEE Main Online Paper (Held On 10 April 2015)

    A) \[0.5\,\overset{\text{o}}{\mathop{\text{A}}}\,\]            

    B) \[1.7\,\overset{\text{o}}{\mathop{\text{A}}}\,\]

    C) \[2.4\,\overset{\text{o}}{\mathop{\text{A}}}\,\]          

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

    Correct Answer: B

    Solution :

     momentum \[P=\sqrt{2mE}\] and \[E=eV\] \[\lambda =\frac{h}{p}=\frac{h}{\sqrt{2mE}}\] \[=\frac{6.6\times {{10}^{-34}}}{\sqrt{2\times 9.1\times {{10}^{-31}}\times 1.6\times {{10}^{-19}}\times 50}}\] \[=1.7\times {{10}^{-10}}M\]                      \[=1.7\,\overset{\text{o}}{\mathop{\text{A}}}\,\]


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