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NEET AIPMT SOLVED PAPER SCREENING 2006

  • question_answer
                    A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?                                                                                                                                                                         

    A)                  1 cm upward

    B)                  4.5 cm downward

    C)                  1 cm downward

    D)                  2 cm upward

    Correct Answer: A

    Solution :

                    Apparent depth of mark as seen through a glass slab of thickness x and refractive index \[\mu \] is                 Apparent depth = \[\frac{\text{Real}\,\text{depth}}{\text{Refractive}\,\text{index}}\]                 \[\text{or}\text{x }\!\!'\!\!\text{ =}\frac{\text{x}}{\mu }=\frac{3}{1.5}=2\,cm\]                 As image appears to be raised by 1 cm, therefore, microscope must be moved upward by 1 cm.


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