Learn

Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctEasyApplication

JEE Main 3 September 2020, Shift 2, Physics Q16

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

Two light waves having the same wavelength λ\lambda in vacuum are in phase initially. Then the first wave travels a path L1L_1 through a medium of refractive index n1n_1 while the second wave travels a path of length L2L_2 through a medium of refractive index n2n_2. After this the phase difference between the two waves is :
  1. (1)2πλ(L1n1−L2n2)\frac{2\pi}{\lambda}\left(\frac{L_1}{n_1} - \frac{L_2}{n_2}\right)
  2. (2)2πλ (n1L1−n2L2)\frac{2\pi}{\lambda}\,(n_1L_1 - n_2L_2)Official answer
  3. (3)2πλ (n2L1−n1L2)\frac{2\pi}{\lambda}\,(n_2L_1 - n_1L_2)
  4. (4)2πλ(L2n1−L1n2)\frac{2\pi}{\lambda}\left(\frac{L_2}{n_1} - \frac{L_1}{n_2}\right)

Official answer

Option 2

NTA final key (Sep 2020).

Chapter
Wave Optics
Topic
Young's Double Slit
Idea tested
Optical Path Length Calculation

Same topic in other shifts

All Young's Double Slit questions
  1. 2 Apr 2026, Shift 2 · Q46In a Young's double slit experiment, the intensity at some point on the screen is found to be 34\frac{3}{4} times of the maximum of the…MediumNumerical value
  2. 4 Apr 2026, Shift 2 · Q50In a double slit experiment, when one of the slits is covered by a transparent mica sheet of refractive index 1.56, the central fringe…MediumNumerical value
  3. 5 Apr 2026, Shift 1 · Q39In Young's double slit experiment, the fringe width of the interference pattern produced on the screen is 2.4 μ2.4\ \mum. If the experiment…EasySingle correct
  4. 5 Apr 2026, Shift 2 · Q42The maximum intensity in a Young's double slit experiment is I0I_0. Distance between the slits (dd) is 5λ5\lambda, where λ\lambda is the…MediumSingle correct
  5. 6 Apr 2026, Shift 1 · Q36In interference experiment the path difference between two interfering waves at a point AA on the screen is λ/3\lambda/3, where λ\lambda…EasySingle correct
  6. 6 Apr 2026, Shift 2 · Q45In a Young double slit experiment, the wavelength of incident light is 6000 Å, the separation between slits S1S_1 and S2S_2 is 5 cm and…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. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.