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Punjab Medical Punjab - MET Solved Paper-2011

  • question_answer
    A single slit is located effectively at infinity in front of a lens of focal length\[1\,\,m\]and it is illuminated   normally   with   light   of wavelength\[600\,\,nm\]. The first minima on either side of central maximum are separated by\[4\,\,mm\]. Width of the slit is

    A) \[0.1mm\]                          

    B) \[0.2mm\]

    C) \[0.3mm\]                          

    D) \[0.4mm\]

    Correct Answer: C

    Solution :

    \[e\sin \theta =\lambda \Rightarrow \sin \theta \approx \theta =\frac{\lambda }{e}\] \[\therefore \]  \[x=f\theta =\frac{f\lambda }{e}\] \[\therefore 2x=\]separation between minima on either side of central maximum                 \[=\frac{2f\lambda }{e}\] \[\therefore \]  \[e=\frac{2f\lambda }{2x}\]                 \[=\frac{2\times 1\times 600\times {{10}^{-9}}}{4\times {{10}^{-3}}}\]                 \[=0.3\,\,mm\]


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