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JEE Main 2019 (9 Apr, Shift 2) · Spherical Surfaces & Thin Lenses

Spherical Surfaces & Thin Lenses question from JEE Main 2019 (9 Apr, Shift 2)

Q92JEE Main 2019 · 9 APR · SHIFT 2Medium

Spherical Surfaces & Thin Lenses

A convex lens of focal length 20 cm produces images of the same magnification 2 when an object is kept at two distances x1 and x2 (x1 > x2) from the lens. The ratio of x1 and x2 is :-

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Answer: (a)

  1. m=ff+um = \frac{f}{f + u} with f=20f = 20 cm.
  2. Real image, m=−2m = -2: 20+u=−10⇒u=−3020 + u = -10 \Rightarrow u = -30 cm, so x1=30x_1 = 30 cm.
  3. Virtual image, m=+2m = +2: 20+u=10⇒u=−1020 + u = 10 \Rightarrow u = -10 cm, so x2=10x_2 = 10 cm.
  4. x1:x2=3:1x_1 : x_2 = 3 : 1. So the answer is (a).
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