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Friday, 9 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 25 July 2021, Shift 1, Physics Q8

Question 8 of 90 in this shift, Physics question 8 of 30, Section A.

In the Young's double slit experiment, the distance between the slits varies in time as d(t)=d0+a0sin⁡ωtd(t)=d_0+a_0\sin\omega t ; where d0d_0, ω\omega and a0a_0 are constants. The difference between the largest fringe width and the smallest fringe width obtained over time is given as :
  1. (1)λDd02a0\frac{\lambda D}{d_0^2}a_0
  2. (2)2λD(d0)(d02−a02)\frac{2\lambda D(d_0)}{\left(d_0^2-a_0^2\right)}
  3. (3)λDd0+a0\frac{\lambda D}{d_0+a_0}
  4. (4)2λDa0(d02−a02)\frac{2\lambda Da_0}{\left(d_0^2-a_0^2\right)}Official answer

Official answer

Option 4

NTA final key.

Chapter
Wave Optics
Topic
Young's Double Slit
Idea tested
YDSE Fringe Width

Same idea in other shifts

Asked 7× in all
  1. 8 Apr 2023, Shift 2 · Q46The width of fringe is 2 mm on the screen in a double slits experiment for the light of wavelength of 400 nm. The width of the fringe for…EasySingle correct
  2. 28 Jul 2022, Shift 1 · Q53In a Young's double slit experiment, a laser light of 560 nm produces an interference pattern with consecutive bright fringes' separation…EasyNumerical value
  3. 29 Jun 2022, Shift 1 · Q49Using Young's double slit experiment, a monochromatic light of wavelength 5000 A˚\mathrm{\AA} produces fringes of fringe width 0.5 mm. If…EasySingle correct
  4. 3 Aug 2021, Shift 2 · Q27In Young's double slit experiment, 58 fringes are observed in the field of view when a light of wavelength 6000 A˚\mathrm{\AA} was used.…EasyNumerical value
  5. 18 Mar 2021, Shift 1 · Q7In Young's double slit arrangement, slits are separated by a gap of 0.5 mm, and the screen is placed at a distance of 0.5 m from them. The…EasySingle correct
  6. 9 Jan 2020, Shift 2 · Q24In a Young's double slit experiment 15 fringes are observed on a small portion of the screen when light of wavelength 500 nm is used. Ten…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 42 of the 174 JEE Main shifts held from 2017 to 2026.