Solve this:
Q. If radii of curvature of both convex surfaces is 20 cm, then focal length of the lens for an object placed in air in the given arrangement is


(1) 10 cm
(2) 20 cm
(3) 40 cm
(4) 80 cm

Dear Student,


use the formual for the refraction through curved surface .1.5v'-1u=1.5-120for second surface4/3v-1.5v'=4/3-1.5-20add both the eqn -1u+4/3v=1.5-120-4/3-1.520-1u+4/3v=130for u=, v=ff=40 cm Regards

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