JEE Main · 2026 · 23 Jan 2026 · Shift 1 · Wave Optics

WhatsApp Email

In two separate Young's double-slit experimental set-ups, two monochromatic light sources of different wavelengths are used to get fringes of equal width. The ratios of the slit separations and that of the wavelengths of light used are

2 : 1

and

1 : 2

respectively. The corresponding ratio of the distances between the slits and the respective screens (

D_{1} / D_{2}

) is ______.

Answer: 4

Solution

The fringe width is

β = \frac{D λ}{d}

. Equal fringe widths require

\frac{D _{1} λ _{1}}{d _{1}} = \frac{D _{2} λ _{2}}{d _{2}}

, so

\frac{D _{1}}{D _{2}} = \frac{λ _{2}}{λ _{1}} \cdot \frac{d _{1}}{d _{2}}

. With

\frac{d _{1}}{d _{2}} = \frac{2}{1}

and

\frac{λ _{1}}{λ _{2}} = \frac{1}{2}

, the ratio is

\frac{D _{1}}{D _{2}} = 2 \times 2 = 4

JEE Main · 2026 · 23 Jan 2026 · Shift 1 · Integer answer

Practise more: all JEE Main PYQs on Wave Optics →

More JEE Main questions on Wave Optics

Given below are two statements:
Statement I: In a Young's double slit experiment, the angular separation of fringes will increase as the screen is moved away from the plane of the slits
Statement II : In a Young's double slit experiment, the angular separation of fringes will inc …
JEE Main 2026View solution →
In a Young's double slit experiment set up, the two slits are kept 0.4 mm apart and screen is placed at 1 m from slits. If a thin transparent sheet of thickness $20 μ m$ is introduced in front of one of the slits then centre bring fringe shifts by 20 mm on the screen …
JEE Main 2026View solution →
When an unpolarized light falls at a particular angle on a glass plate (placed in air), it is observed that the reflected beam is linearly polarized. The angle of refracted beam with respect to the normal is $____$ .
( $tan^{- 1} (1.52) = 57. 7^{\circ}$ , refractive indices of air a …
JEE Main 2026View solution →
Given below are two statements:

Statement-I: A plane wave after passing through prism remains as plane wave but passing through small pin hole may become spherical wave.
Statement-II: The curvature of a spherical wave emerging from a slit will increase for increasing slit width. …
JEE Main 2026View solution →
In the Young's double slit experiment the intensity produced by each one of the individual slits is $I_{0}$ . The distance between two slits is 2 mm. The distance of screen from slits is 10 m. The wavelength of light is $6000 \overset{˚}{A}$ . The intensity of light on the screen in front of …
JEE Main 2026View solution →
A beam of light consisting of wavelengths 650 nm and 550 nm illuminates the Young's double slits with separation of 2 mm such that the interference fringes are formed on a screen, placed at a distance of 1.2 m from the slits. The least distance of a point from the central maximum …
JEE Main 2026View solution →