NEET Physics Wave Optics / तरंग प्रकाशिकी NEET PYQ-Wave Optics

  • question_answer
    Two slits in Youngs experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern \[\frac{{{I}_{\max }}}{{{I}_{\min }}}\] is                                               [NEET (Re) 2015]

    A)  \[\frac{9}{4}\] 

    B)  \[\frac{121}{49}\]

    C)  \[\frac{49}{121}\]                    

    D)       \[\frac{4}{9}\]

    Correct Answer: A

    Solution :

               
    Given, In YDSE experiment, having two slits of width in the ratio of 1 : 25
    So, ratio of intensity,
    \[\frac{{{I}_{1}}}{{{I}_{2}}}=\frac{{{W}_{1}}}{{{W}_{2}}}=\frac{1}{25}\Rightarrow \frac{{{I}_{2}}}{{{I}_{1}}}=\frac{25}{1}\]
    \[\therefore \]      \[\frac{{{I}_{\max }}}{{{I}_{\max }}}=\frac{{{(\sqrt{{{I}_{2}}}+\sqrt{{{I}_{1}}})}^{2}}}{{{(\sqrt{{{I}_{2}}}-\sqrt{{{I}_{1}}})}^{2}}}={{\left[ \frac{\sqrt{\frac{{{I}_{2}}}{{{I}_{1}}}}+1}{\sqrt{\frac{{{I}_{2}}}{{{I}_{1}}}}-1} \right]}^{2}}\]
    \[\Rightarrow \]   \[{{\left[ \frac{5+1}{5-1} \right]}^{2}}={{\left( \frac{6}{4} \right)}^{2}}=\frac{36}{16}=\frac{9}{4}\]
    Thus,    \[\frac{{{I}_{\max }}}{{{I}_{\min }}}=\frac{9}{4}\]


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