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JEE Main & Advanced Physics Ray Optics Question Bank Refraction at Curved Surface

  • question_answer
    A double convex lens of focal length 20 cm is made of glass of refractive index 3 / 2. When placed completely in water \[{{(}_{a}}{{\mu }_{w}}=4/3)\], its focal length will be [CBSE PMT 1990; MP PMT/PET 1998]

    A)            80 cm                                      

    B)            15 cm

    C)            17.7 cm                                   

    D)            22.5 cm

    Correct Answer: A

    Solution :

               \[{{f}_{water}}=4\times {{f}_{air}}\], air lens is made up of glass.


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