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Saturday, 31 October

JEE Main 2024 · PhysicsNumerical answerNumerical valueMediumData or graph

JEE Main 30 January 2024, Shift 2, Physics Q59

Question 59 of 90 in this shift, Physics question 29 of 30, Section B.

In an experiment to measure the focal length (ff) of a convex lens, the magnitude of object distance (xx) and the image distance (yy) are measured with reference to the focal point of the lens. The yy-xx plot is shown in figure. The focal length of the lens is ________ cmcm.

The figure, in words

Graph of y (cm, vertical, ticks 10-40) vs x (cm, horizontal, ticks 10-40): a descending curve through plotted points A, B, C, D, E (A near x=20,y~35; B near x=20,y~28; C near x=22,y~22; D and E further right near y~10 where the curve flattens); dashed guide lines from the axes to point C.

Official answer

20

NTA final key.

Chapter
Ray Optics and Optical Instruments
Topic
Lens Maker's Formula
Idea tested
v versus u Graph

Same idea in other shifts

Asked 3× in all
  1. 4 Aug 2021, Shift 2 · Q4The reported graph shows the variation of ‘v’ with ‘u’, where ‘u’ represents the distance of the object from the lens and v represent the…MediumDiagram basedHas a figure
  2. 5 Sep 2020, Shift 1 · Q17For a concave lens of focal length ff, the relation between object and image distances u and vv, respectively, from its pole can best be…MediumDiagram basedHas a figure

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.