JEE Main & Advanced Physics Ray Optics Sample Paper Topic Test - Refraction of Light Through Plane Surfaces

  • question_answer
    A prism of dispersive power 0.021 and refractive index 1.53 form an achromatic combination with prism of angle \[4.2{}^\circ \] and dispersive power 0.045 having refractive index 1.65. Find the resultant deviation.

    A) \[1.12{}^\circ \]

    B) \[2.16{}^\circ \]

    C) \[3.12{}^\circ \]

    D) \[4.18{}^\circ \]

    Correct Answer: C

    Solution :

    [c] Here, \[\omega =0.021;\,\,\mu =1.53;\,\,\omega '=0.045;\]
                            \[\mu '=1.65;\] \[A'={{4.2}^{o}}\] 
    For no dispersion, \[\omega \delta \,+\,\delta '\,\delta '=0\]
    or         \[\omega A(\mu -1)+\omega 'A'(\mu -1)=0\]
    or         \[A=-\frac{\omega 'A'(\mu '-1)}{\theta (\mu -1)}\]
                \[=\frac{0.045\times 4.2(1.65-1)}{0.02\times (1.53-1)}=-{{11.04}^{o}}\]
    Net deviation,
                \[\delta +\delta '=A(\mu -1)+A'(\mu '-1)\]
                \[=-11.04(1.53-1)+4.2(1.65-1)\]
                \[=-11.04\times 0.53+4.2\times 0.65\]
                \[=-5.85+2.73={{3.12}^{o}}\]


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