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JEE Main & Advanced Physics Ray Optics Question Bank Mock Test - Geometrical Optics

  • question_answer
    A lens forms a real image of an object. The distance from the object to the lens is x cm and that from the lens to the image is y cm. The graph (see figure) shows the variation of y with x. It can be deduced that the lens is

    A) Converging and of focal length 10 cm

    B) Converging and of focal length 20 cm

    C) Converging and of focal length 40 cm

    D) Diverging and of focal length 20 cm

    Correct Answer: A

    Solution :

    [a] A diverging lens is ruled out because both x and y are positive values. Both x and y equal 20 cm at their smallest sum, which occurs when \[x+y=40cm=4f\] \[\therefore f=10cm\] This indicates a converging lens of focal length=10cm


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