In diffraction, dsin30∘=λ, λ=2d
Young’s fringe width [ d′- the separation between two slits]
β=d′λ×D⇒10−2=2d×d′50×10−2
⇒10−2=2×d′10−6×50×10−2⇒d′=25μm.
The angular width of the central maximum in a single slit diffraction pattern is 60° . The width of the slit is 1μ m. The slit is illuminated by…
JEE Main 2018 — Physics Optics
2018mcqhard
The angular width of the central maximum in a single slit diffraction pattern is 60∘ . The width of the slit is 1μm. The slit is illuminated by monochromatic plane waves. If another slit of the same width is made near it, Young's fringes can be observed on a screen placed at a distance 50cm from the slits. If the observed fringe width is 1cm, what is slit separation distance? (i.e., the distance between the centres of each slit.)
Official previous-year question
Held on 8 Apr 2018 · Verified 6 Jul 2026.
Options
- A
100μm
- B
25μm
- C
50μm
- D
75μm
Did you get this right?
Sign in to track your attempts and accuracy.
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.
JEE Main Optics in other years
More JEE Main Optics questions
In a microscope of tube length 10 cm two convex lenses are arranged with focal length of 2 cm and 5 cm. Total magnification obtained with this system for normal adjustment is $(5)^{k}$. The value of $k$ is $\_\_\_\_$.
2026easy
In Young's double slit experiment, the fringe width of the interference pattern produced on the screen is $2.4$ $\mu$m. If the experiment is carried out in another medium having refractive index $1.2$, the fringe width will be _____ $\mu$m.
2026easy
The magnitudes of power of a biconvex lens (refractive index 1.5) and that of a plano-concave lens (refractive index $=1.7$) are same. If the curvature of planoconcave lens exactly matches with the curvature of back surface of the biconvex lens, then ratio of radius of curvature of front and back surface of the biconvex lens is $\_\_\_\_$.
2026medium
The exit surface of a prism with refractive index $n$ is coated with a material having refractive index $\frac{n}{2}$. When this prism is set for minimum angle of deviation, it exactly meets the condition of critical angle. The prism angle is $\_\_\_\_$.
2026medium
An unpolarized light of certain intensity passes through a combination of two polarizers whose transmission axes are at $30°$ and $90°$, respectively, with respect to the horizontal axis. A third polarizer with its transmission axis at $60°$ with the horizontal axis is placed between the two existing polarizers. The ratio of the output intensities with and without the third polarizer is ______.
2026medium
Other Physics topics for JEE Main
Keep practicing Optics
Work through every JEE Main Optics PYQ, year by year.