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Saturday, 10 October

JEE Main 2020 · PhysicsNumerical answerNumerical valueEasyCalculation

JEE Main 8 January 2020, Shift 1, Physics Q25

Question 25 of 75 in this shift, Physics question 25 of 25, Section B.

A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is 30 cm and the refractive index of the lens material is 1.5, then the focal length of the lens (in cm) is ______.

Official answer

60.00

NTA final key (Jan 2020).

Chapter
Ray Optics and Optical Instruments
Topic
Lens Maker's Formula
Idea tested
Plano-Convex Lens Focal Length

Same idea in other shifts

Asked 2× in all
  1. 6 Sep 2020, Shift 2 · Q17A double convex lens has power P and same radii of curvature R of both the surfaces. The radius of curvature of a surface of a…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. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.