In an interference experiment the ratio of amplitudes of coherent waves is $\frac{\mathrm{a}_{1}}{\mathrm{a}_{2}}=\frac{1}{3}$. The ratio of maximum and minimum intensities of fringes will be:

JEE Main · 2019 · 08 Apr 2019 · Shift 1 · Wave Optics

In an interference experiment the ratio of amplitudes of coherent waves is

\frac{a _{1}}{a _{2}} = \frac{1}{3}

. The ratio of maximum and minimum intensities of fringes will be:

(A)9
(B)4✓ Correct
(C)18
(D)2

Answer: (B)

Solution

The amplitude ratio is

\frac{a _{1}}{a _{2}} = \frac{1}{3}

, and since the fringe extremes depend on the sum and difference of amplitudes, the maximum-to-minimum intensity ratio is

\frac{I _{m a x}}{I _{m i n}} = (\frac{a _{2} + a _{1}}{a _{2} - a _{1}})^{2} = (\frac{3 + 1}{3 - 1})^{2} = (\frac{4}{2})^{2} = 4

JEE Main · 2019 · 08 Apr 2019 · Shift 1 · Single correct option

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 →
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 correspo …
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 →