JCECE Medical JCECE Medical Solved Paper-2003

  • question_answer
    A ray of light is incident on a surface of a plate of glass of refractive index 1.5 at polarising angle. The angle of refraction of the ray will be:

    A) \[{{53.7}^{o}}\]          

    B) \[~{{43.7}^{o}}\]

    C) \[{{33.7}^{o}}\]          

    D)  none of these    

    Correct Answer: C

    Solution :

     Key Idea: Apply Brewsters law. According to Brewsters law, when unpolarised light is incident at an angle called polarizing angle, \[{{i}_{p}}\]on an interface separating air from a medium of refractive index \[n,\]then the reflected light is fully polarised (perpendicular to the plane of incidence), provided \[n=\tan {{i}_{p}}\] Given, \[n=1.5\] \[\therefore \] \[1.5=\tan {{i}_{p}}\] \[\Rightarrow \] \[{{i}_{p}}={{\tan }^{-1}}(1.5)={{56.3}^{o}}\] If r is the angle of refraction them \[{{i}_{p}}+r={{90}^{o}}\] \[\Rightarrow \] \[r=9+{{90}^{o}}-{{i}_{p}}\] \[={{90}^{o}}-{{56.3}^{o}}={{33.7}^{o}}.\]


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