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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumConceptual

JEE Main 3 August 2021, Shift 1, Physics Q15

Question 15 of 90 in this shift, Physics question 15 of 30, Section A.

In the given figure, a ray of light passes through four transparent media with refractive indices n1n_1, n2n_2, n3n_3 and n4n_4. The surfaces of all the media are parallel. If the emergent ray CD is parallel to the incident ray AB, we must have -

The figure, in words

A rectangle divided by three vertical lines into four adjacent vertical slabs labelled n1, n2, n3, n4 from left to right. A ray enters at A at the bottom left in the n1 slab and travels (arrow) slightly upward to B on the n1/n2 boundary near the bottom; from B it bends to a steeper upward path through n2 and n3 to C on the n3/n4 boundary; from C it continues nearly horizontally through n4 to D just outside the right edge, with arrows on the segments.
  1. (1)n1=n2n_1 = n_2
  2. (2)n2=n3n_2 = n_3
  3. (3)n3=n4n_3 = n_4
  4. (4)n4=n1n_4 = n_1Official answer

Official answer

Option 4

NTA final key.

Chapter
Ray Optics and Optical Instruments
Topic
Refraction and Snell's Law
Idea tested
Normal Shift across Multiple Slabs

Same topic in other shifts

All Refraction and Snell's Law questions
  1. 8 Apr 2026, Shift 2 · Q42Light ray incident along a vector AO→\overrightarrow{AO} (AO→=2i^−3j^)\left(\overrightarrow{AO} = 2\hat{i} - 3\hat{j}\right) emerges out along vector…MediumDiagram basedHas a figure
  2. 3 Apr 2025, Shift 2 · Q42A monochromatic light of frequency 5×10145 \times 10^{14} Hz travelling through air, is incident on a medium of refractive index '2'.…EasySingle correct
  3. 4 Apr 2025, Shift 2 · Q47If an optical medium possesses a relative permeability of 10π\frac{10}{\pi} and relative permittivity of 10.0885\frac{1}{0.0885}, then the…MediumNumerical value
  4. 7 Apr 2025, Shift 1 · Q50A container contains a liquid with refractive index of 1.2 up to a height of 60 cm and another liquid having refractive index 1.6 is added…MediumNumerical value
  5. 7 Apr 2025, Shift 2 · Q41Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Refractive…EasyAssertion–reason
  6. 7 Apr 2025, Shift 2 · Q42A transparent block A having refractive index μ=1.25\mu=1.25 is surrounded by another medium of refractive index μ=1.0\mu=1.0 as shown in figure.…MediumSingle correctHas 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.