JCECE Medical JCECE Medical Solved Paper-2015

  • question_answer
    A vector of magnitude \[|\psi |\] is turned through angle \[\frac{\text{o }\!\!|\!\!\text{ }}{2}.\] The magnitude of change in the vector is given by

    A)  \[2|\psi ||cos\,o|/4|\]

    B)  \[|\psi ||sino|/4|\]

    C)  \[|\psi {{|}^{2}}|sino|/4{{|}^{2}}\]

    D)  \[2|\psi ||sino|/4|\]

    Correct Answer: D

    Solution :

     Let\[\text{ }\!\!\psi\!\!\text{ }\] is rotated through angle \[\frac{\text{o}|}{2}\] to get \[\eta .\] \[\therefore \]\[\text{ }\!\!|\!\!\text{  }\!\!\psi\!\!\text{  }\!\!|\!\!\text{ = }\!\!|\!\!\text{  }\!\!\eta\!\!\text{  }\!\!|\!\!\text{ }\]and angle between\[\text{ }\!\!\psi\!\!\text{ }\]and \[\eta \]is \[\text{o }\!\!|\!\!\text{ /2}\text{.}\] \[\therefore \]Magnitude of the change in vector\[\text{ }\!\!\psi\!\!\text{ }\] is \[|\eta -\psi |=\sqrt{|\eta {{|}^{2}}|\psi {{|}^{2}}+2|\eta ||\psi |cos\left( \pi -\frac{\text{o}|}{2} \right)}\] \[=|\psi |\sqrt{2(1-coso|/2)}\] \[=|\psi |\times \,\sqrt{2\times 2{{\sin }^{2}}\text{o }\!\!|\!\!\text{ /4}}\] \[=|\psi |\times 2\sin \text{o}|/4=2|\psi ||sino|/4|\]


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