JEE Main & Advanced Physics Ray Optics Sample Paper Topic Test - Refraction of Light Through Curved Surfaces

  • question_answer
    A convex lens forms a real image three times larger than the object on a screen. Object and screen are moved until the image becomes twice the size of the object. If the shift of the object is 6 cm. The shift of screen is:

    A) 36 cm

    B) 72 cm

    C) 18 cm

    D) 9 cm

    Correct Answer: A

    Solution :

    [a] \[\frac{1}{3x}+\frac{1}{x}=\frac{1}{f}\]
    or         \[\frac{4}{3x}=\frac{1}{f}\] ...(i)
    or         \[\frac{3}{2(6+x)}=\frac{1}{f}\] ...(ii)
    (i) and (ii) gives \[\frac{4}{3x}=\frac{3}{2(6+x)}\]
    \[\therefore \]      \[9x=48+8x\]
                \[x=4\text{8 cm}\]
    Shift of screen \[=3x-2(6+x)\]\[=3\times 48-2(6+48)\]\[=3\text{6 cm}\]

You need to login to perform this action.
You will be redirected in 3 sec spinner