JEE Main & Advanced Physics Question Bank Prism Theory and Dispersion of Light

  • question_answer
    Three prisms of crown glass, each have angle of prism 9° and two prisms of flint glass are used to make direct vision spectroscope. What will be the angle of flint glass prisms if \[\mu \] for flint is 1.60 and \[\mu \] for crown glass is 1.53

    A)            11.9°                                        

    B)            16.0°

    C)            15.3°                                        

    D)            9.11°

    Correct Answer: A

    Solution :

                       Total deviation = 0                    \[{{\delta }_{1}}+{{\delta }_{2}}+{{\delta }_{3}}+{{\delta }_{4}}+{{\delta }_{5}}=({{\mu }_{1}}-1)\,{{A}_{1}}-({{\mu }_{2}}-1)\,{{A}_{2}}\]                    \[+({{\mu }_{3}}-1)\,{{A}_{3}}-({{\mu }_{4}}-1)\,{{A}_{4}}+({{\mu }_{5}}-1)\,{{A}_{5}}=0\]                    \[\Rightarrow \]\[2\times {{A}_{2}}(1.6-1)=3\,(1.53-1)\,9\]            \[\Rightarrow \]\[{{A}_{2}}=3\left( \frac{0.53\times 9}{1.2} \right)={{11.9}^{o}}\] 


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