JEE Main & Advanced Sample Paper JEE Main - Mock Test - 24

  • question_answer
    If the intercepts made by the plane \[\vec{r}.n=q\] on x, y and z axes are \[{{a}_{1}},{{a}_{2}}\] and \[{{a}_{3}}\] respectively, then

    A) \[\vec{n}=(q{{a}_{1}})\hat{i}+(q{{a}_{2}})\hat{j}+(q{{a}_{3}})\hat{k}\]

    B) \[\vec{n}=\frac{{{a}_{1}}}{q}\hat{i}+\frac{{{a}_{2}}}{q}\hat{j}+\frac{{{a}_{3}}}{q}\hat{k}\]

    C) \[\vec{n}=\frac{q}{{{a}_{1}}}\hat{i}+\frac{q}{{{a}_{2}}}\hat{j}+\frac{q}{{{a}_{3}}}\hat{k}\]

    D)  \[\vec{n}=\left( \frac{1}{{{a}_{1}}q} \right)\hat{i}+\left( \frac{1}{{{a}_{2}}q} \right)\hat{j}+\left( \frac{1}{{{a}_{3}}q} \right)\hat{k}\]

    Correct Answer: C

    Solution :

    [c] For x-axis \[\vec{r}={{a}_{i}}\hat{i}\,\,\,\,\Rightarrow \,\,\,\,\vec{n}.\hat{j}=\frac{q}{{{a}_{1}}}\] Similarly for y-axis, \[\vec{n}.\hat{j}=\frac{q}{{{a}_{2}}}\] And for z-axis \[\vec{n}.\vec{k}=\frac{q}{{{a}_{3}}}\] \[\therefore \,\,\,\vec{n}=(\vec{n}.\hat{i})\hat{i}+(\vec{n}.\hat{j})\hat{j}+(\vec{n}.\hat{k})\hat{k}\] \[\therefore \,\,\,\vec{n}=\frac{q}{{{a}_{1}}}\hat{i}+\frac{q}{{{a}_{2}}}\hat{j}+\frac{q}{{{a}_{3}}}\hat{k}\]


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