JEE Main & Advanced JEE Main Paper (Held On 12-Jan-2019 Morning)

  • question_answer
    A particle A of mass m and charge q is accelerated by a potential difference of 50 V. Another particle B of mass 4 m and charge q is accelerated by a potential difference of 2500 V. The ratio of de-Broglie wavelengths\[\frac{{{\lambda }_{A}}}{{{\lambda }_{B}}}\] is close to [JEE Main Online Paper Held On 12-Jan-2019 Morning]

    A) 14.14                           

    B) 0.07  

    C) 4.47                 

    D)   10.00

    Correct Answer: A

    Solution :

    For particle A \[{{m}_{1}}=m,{{q}_{1}}=q;{{V}_{1}}=50\,V\] \[{{\lambda }_{A}}=\frac{h}{\sqrt{2{{m}_{1}}{{q}_{1}}{{V}_{1}}}}\]                                   ?.(i) For particle B \[{{m}_{2}}=4m,{{q}_{2}}=q;{{V}_{2}}=2500\,V\] \[{{\lambda }_{B}}=\frac{h}{\sqrt{2{{m}_{2}}{{q}_{2}}{{V}_{2}}}}\]                                   ...(ii) Dividing eqn. (i) by (ii), \[\frac{{{\lambda }_{A}}}{{{\lambda }_{B}}}=\sqrt{\frac{{{m}_{2}}{{q}_{2}}{{v}_{2}}}{{{m}_{1}}{{q}_{1}}{{v}_{1}}}}=\sqrt{\frac{4m\times q\times 2500}{m\times q\times 50}}\] \[\frac{{{\lambda }_{A}}}{{{\lambda }_{B}}}=\sqrt{\frac{4\times 2500}{50}}=14.14\]


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