JEE Main & Advanced Sample Paper JEE Main Sample Paper-13

  • question_answer
    A ray of light travels along the line \[2x-3y+5=0\] and strikes a plane mirror lying along the line\[x+y=2\]. The equation of the straight line containing the refracted ray is

    A)  \[2x-3y+3=0\]  

    B)  \[3x-2y+3=0\]

    C)  \[21x-7y+1=0\]

    D)  \[21x+7y-1=0\]

    Correct Answer: B

    Solution :

     The point of intersecton of \[{{x}_{1}},\,{{x}_{2}},\,{{x}_{3}}\] and \[{{k}_{1}},\,{{k}_{2}},\,{{k}_{3}},\,{{k}_{4}}....,\] is \[{{x}_{5}}={{x}_{1}}+{{x}_{2}}+{{x}_{3}}+...\] \[\Rightarrow \] Point \[\frac{mg}{{{k}_{s}}}=mg\,\left( \frac{1}{{{k}_{1}}}+\frac{1}{{{k}_{2}}}+\frac{1}{{{k}_{3}}}+... \right)\] is the point of incidence. \[\therefore \] Slope of incident ray \[\frac{1}{{{k}_{s}}}-\frac{1}{{{k}_{1}}}+\frac{1}{{{k}_{2}}}+\frac{1}{{{k}_{3}}}+...\] and Slope of normal = 1 Let slope of refracted ray be m. Then, \[{{k}_{1}}=k,\] \[{{k}_{2}}=2k,\]               \[{{k}_{3}}=3k,...\]                                           \[\frac{1}{{{k}_{s}}}=\frac{1}{k}+\frac{1}{2k}+\frac{1}{4k}+\frac{1}{8k}+...\] The equation of the striaght line containing the refracted ray is \[\Rightarrow \] \[\frac{1}{{{k}_{s}}}=\frac{1}{k}\,\left( 1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+... \right)\] \[\Rightarrow \]


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