JEE Main 2020 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 8 January 2020, Shift 1, Physics Q16

Question 16 of 75 in this shift, Physics question 16 of 25, Section A.

The magnifying power of a telescope with tube length 60 cm is 5. What is the focal length of its eye piece ?

(1)10 cmOfficial answer
(2)20 cm
(3)30 cm
(4)40 cm

Official answer

Option 1

NTA final key (Jan 2020).

Chapter: Ray Optics and Optical Instruments
Topic: Optical Instruments
Idea tested: Telescope Tube Length

Same topic in other shifts

All Optical Instruments questions

4 Apr 2026, Shift 1 · Q44A telescope with objective diameter $R$ is used to observe a distant star emitting light of wavelength $500$ nm, at a resolution of…EasySingle correct
5 Apr 2026, Shift 1 · Q42A compound microscope is designed with two symmetric biconvex lenses. The objective lens is cut vertically, creating two identical…HardSingle correct
28 Jul 2022, Shift 1 · Q46In normal adjustment, for a refracting telescope, the distance between objective and eye piece is 30 cm. The focal length of the…EasySingle correct
3 Aug 2021, Shift 2 · Q15To view a small object with angular magnification 5, the power of the microscope needed is [The final image is formed at infinity]…EasySingle correct
3 Aug 2021, Shift 2 · Q16If a man having the least distance of distinct vision of 50 cm, what should be the focal length of the spectacles for the man ?EasySingle correct
18 Mar 2021, Shift 1 · Q16Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her as non-uniform…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.