Ray Optics

JEE Main level, single correct, medium

183 of 295

Question 183 of 295

Find the distance of the image from object O,O, formed by the combination of lenses in the figure:

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Answer: (A) 75cm75cm

(1)\left(1\right) Lens formula
1v−1u=1f,\dfrac{1}{v}-\dfrac{1}{u}=\dfrac{1}{f},
1v−1−30=110\dfrac{1}{v}-\dfrac{1}{-30}=\dfrac{1}{10}
1v=110−130;1v=3−130;v=15cm\dfrac{1}{v}=\dfrac{1}{10}-\dfrac{1}{30};\dfrac{1}{v}=\dfrac{3-1}{30};v=15cm
(2)\left(2\right) u=+10u=+10
1v−110=1−10\dfrac{1}{v}-\dfrac{1}{10}=\dfrac{1}{-10}
1v=−110+110v=∞\dfrac{1}{v}=\dfrac{-1}{10}+\dfrac{1}{10}v=\infty
(3)\left(3\right) Ray will converge at focus of 30 cm right of third lens.
it.v=+30cmv=+30cm (from third lens)

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