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MHT CET 2026 (12 May, Shift 1) · Combination of Lenses

Combination of Lenses question from MHT CET 2026 (12 May, Shift 1)

Q9MHT CET 2026 · 12 MAY · SHIFT 1Medium

Combination of Lenses

A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index of the first lens is 1.51.5 and that of second is 1.21.2. Both the curved surfaces are of the same radius of curvature R=14R = 14 cm. For an object distance of 4040 cm, the image distance will be

Figure

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Answer: (d)

  1. Two plano-convex lenses in contact: P=n1−1R+n2−1R=0.5+0.214=120P = \frac{n_1-1}{R} + \frac{n_2-1}{R} = \frac{0.5 + 0.2}{14} = \frac{1}{20}
  2. So f=20 cmf = 20\text{ cm}; the object at 40 cm=2f40\text{ cm} = 2f.
  3. Image at 2f2f: v=40 cmv = 40\text{ cm}.
  4. So the answer is (d) 40.0 cm.
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