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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumMulti-step

JEE Main 27 August 2021, Shift 1, Physics Q17

Question 17 of 90 in this shift, Physics question 17 of 30, Section A.

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

The figure, in words

Object O (upright arrow on the axis) at left; three lenses in a row on the axis: a convex lens with f=+10f=+10 cm at 30 cm from O, a concave lens with f=−10f=-10 cm at 5 cm after it, and a convex lens with f=+30f=+30 cm at 10 cm after the concave lens.
  1. (1)10 cm
  2. (2)20 cm
  3. (3)75 cmOfficial answer
  4. (4)infinity

Official answer

Option 3

NTA final key.

Chapter
Ray Optics and Optical Instruments
Topic
Lens Maker's Formula
Idea tested
Lenses Separated by a Distance

Same idea in other shifts

Asked 6× in all
  1. 5 Apr 2026, Shift 2 · Q41An object ABAB is placed 15 cm on the left of a convex lens PP of focal length 10 cm. Another convex lens QQ is now placed 15 cm right…MediumSingle correct
  2. 7 Apr 2025, Shift 1 · Q27Two thin convex lenses of focal lengths 30 cm and 10 cm are placed coaxially, 10 cm apart. The power of this combination is:EasySingle correct
  3. 8 Apr 2024, Shift 2 · Q45The position of the image formed by the combination of lenses is :MediumDiagram basedHas a figure
  4. 12 Apr 2023, Shift 1 · Q59Two convex lenses of focal length 20 cm each are placed coaxially with a separation of 60 cm between them. The image of the distant object…MediumNumerical value
  5. 2 Apr 2017 (offline) · Q22A diverging lens with magnitude of focal length 25 cm is placed at a distance of 15 cm from a converging lens of magnitude of focal length…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.