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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    The exposure time of a camera lens at the \[\frac{f}{2.8}\]setting is \[\frac{1}{200}\]sec. The correct time of exposure at \[\frac{f}{5.6}\] is

    A)  0.02 s             

    B)  0.2 s

    C)  0.4 s              

    D)  0.04 s

    Correct Answer: A

    Solution :

     Time of exposure\[\propto {{(f\,number)}^{2}}\]\[\Rightarrow \]\[\frac{{{t}_{2}}}{{{t}_{1}}}={{\left[ \frac{5.6}{2.8} \right]}^{2}}=4\] \[{{t}_{2}}=4{{t}_{1}}=4\times \frac{1}{200}=\frac{1}{50}s=0.02\,s\]


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