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JEE Main & Advanced Sample Paper JEE Main Sample Paper-28

  • question_answer
    A light ray is incident perpendicular to one face of a \[{{90}^{o}}\] prism and is totally internally reflected at the glass - air interface. If the angle of reflection is\[{{45}^{o}}\]. We conclude that the refractive index is :

    A)  \[n<\frac{1}{\sqrt{2}}\]                               

    B)  \[n<\sqrt{2}\]

    C)  \[n>\sqrt{\frac{1}{\sqrt{2}}}\]                  

    D)  \[n<\sqrt{2}\]

    Correct Answer: B

    Solution :

    For total internal reflection to take place, \[{{\theta }_{c}}<{{45}^{o}}\]or\[\sin {{\theta }_{c}}<\frac{1}{\sqrt{2}}\] \[\Rightarrow \frac{1}{n}<\frac{1}{\sqrt{2}}\,\,\therefore n>\sqrt{2}\]


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