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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 25 July 2021, Shift 2, Physics Q17

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

A prism of refractive index μ\mu and angle of prism A is placed in the position of minimum angle of deviation. If minimum angle of deviation is also A, then in terms of refractive index value of A is :
  1. (1)sin⁡−1(μ2)\sin^{-1}\left(\frac{\mu}{2}\right)
  2. (2)sin⁡−1(μ−12)\sin^{-1}\left(\sqrt{\frac{\mu - 1}{2}}\right)
  3. (3)2cos⁡−1(μ2)2\cos^{-1}\left(\frac{\mu}{2}\right)Official answer
  4. (4)cos⁡−1(μ2)\cos^{-1}\left(\frac{\mu}{2}\right)

Official answer

Option 3

NTA final key.

Chapter
Ray Optics and Optical Instruments
Topic
Prism Deviation
Idea tested
Minimum Deviation Condition

Same idea in other shifts

Asked 9× in all
  1. 2 Apr 2026, Shift 1 · Q40For a thin symmetric prism made of glass (refractive index 1.51.5), the ratio of incident angle and minimum deviation will be _________.MediumSingle correct
  2. 5 Apr 2026, Shift 1 · Q40A ray of light passing through an equilateral prism is having velocity 2.12×1082.12 \times 10^8 m/s in the prism material, then the minimum…MediumSingle correct
  3. 3 Apr 2025, Shift 1 · Q41Consider following statements for refraction of light through prism, when angle of deviation is minimum. A. The refracted ray inside prism…MediumOther
  4. 6 Apr 2024, Shift 1 · Q51The refractive index of prism is μ=3\mu = \sqrt{3} and the ratio of the angle of minimum deviation to the angle of prism is one. The value…MediumNumerical value
  5. 27 Jan 2024, Shift 1 · Q45If the refractive index of the material of a prism is cot⁡(A2)\cot\left(\frac{A}{2}\right), where A is the angle of prism then the angle of…MediumSingle correct
  6. 31 Jan 2024, Shift 1 · Q45The refractive index of a prism with apex angle AA is cot⁡A/2\cot A/2. The angle of minimum deviation is :MediumSingle correct
  7. 30 Jun 2022, Shift 1 · Q58The refractive index of an equilateral prism is 2\sqrt{2} . The angle of emergence under minimum deviation position of prism, in degree,…EasyNumerical value
  8. 22 Jul 2021, Shift 2 · Q24A ray of light passing through a prism (μ=3\mu = \sqrt{3}) suffers minimum deviation. It is found that the angle of incidence is double the…EasyNumerical value

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 108 of the 174 JEE Main shifts held from 2017 to 2026.