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NEET 2002 (AIPMT) · Spherical Surfaces & Thin Lenses

Spherical Surfaces & Thin Lenses question from NEET 2002 (AIPMT)

Q109NEET 2002 · AIPMTMedium

Spherical Surfaces & Thin Lenses

A bulb is located on a wall. Its image is to be obtained on a parallel wall with the help of convex lens. The lens is placed at a distance d ahead of second wall, then required focal length will be

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Answer: (b)

  1. The intended case is an image of equal size, so ∣u∣=v=2f|u| = v = 2f.
  2. Lens to second wall is the image distance: d=2fd = 2f.
  3. f=d2f = \frac{d}{2}
  4. So the answer is (b) only d2\frac{d}{2}.
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