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Wave Optics

22 JEE Main questions · Physics

Interference

  1. PhysicsJEE Main 21 Jan 2026, Shift 1·Q11·MCQ·Easy–moderate
    Open
    In a double slit experiment the distance between the slits is 0.1 cm and the screen is placed at 50 cm from the slits plane. When one slit is covered with a transparent sheet having thickness tt and refractive index n (=1.5)n\,(=1.5), the central fringe shifts by 0.2 cm. The value of tt is cm.
    1. (1)8×10−48\times10^{-4}
    2. (2)6.0×10−36.0\times10^{-3}
    3. (3)5.6×10−45.6\times10^{-4}
    4. (4)5.0×10−35.0\times10^{-3}
  2. PhysicsJEE Main 21 Jan 2026, Shift 2·Q9·MCQ·Easy–moderate
    Open

    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 increase when monochromatic source is replaced by another monochromatic source of higher wavelength

    In the light of the above statements, choose the correct answer from the options given below:

    1. (1)Both Statement I and Statement II are true
    2. (2)Both Statement I and Statement II are false
    3. (3)Statement I is false but Statement II is true
    4. (4)Statement I is true but Statement II is false
  3. PhysicsJEE Main 21 Jan 2026, Shift 2·Q24·Numerical·Easy–moderate
    Open
    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\mum is introduced in front of one of the slits then central bright fringe shifts by 20 mm on the screen. The refractive index of transparent sheet is given by α10\dfrac{\alpha}{10}, where α\alpha is .
    We corrected a printing error in the original paper

    Source printed “0.4. mm”; “centre bring fringe”.

  4. PhysicsJEE Main 23 Jan 2026, Shift 1·Q24·Numerical·Easy–moderate
    Open
    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 (D1/D2)(D_1/D_2) is .
  5. PhysicsJEE Main 24 Jan 2026, Shift 2·Q17·MCQ·Easy–moderate
    Open
    In the Young's double slit experiment the intensity produced by each one of the individual slits is I0I_0. The distance between two slits is 2 mm. The distance of screen from slits is 10 m. The wavelength of light is 6000 Å. The intensity of light on the screen in front of one of the slits is .
    1. (1)2I02I_0
    2. (2)I0I_0
    3. (3)I02\dfrac{I_0}{2}
    4. (4)4I04I_0
  6. PhysicsJEE Main 28 Jan 2026, Shift 2·Q24·Numerical·Moderate
    Open
    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, where the bright fringes due to both the wavelengths coincide, is ×10−5\times10^{-5} m.
  7. PhysicsJEE Main 2 Apr 2026, Shift 2·Q21·Numerical·Easy–moderate
    Open
    In a Young's double slit experiment, the intensity at some point on the screen is found to be 34\dfrac34 times of the maximum of the interference pattern. The path difference between the interfering waves at this point is λx\dfrac{\lambda}{x} where λ\lambda is wavelength of the incident light. The value of xx is .
  8. PhysicsJEE Main 4 Apr 2026, Shift 2·Q25·Numerical·Easy–moderate
    Open
    In a double slit experiment, when one of the slits is covered by a transparent mica sheet of refractive index 1.56, the central fringe shifts to the position of 7th7^{\text{th}} bright fringe, obtained with both slits uncovered. If the light source wavelength is 450 nm, the thickness of mica sheet is α×10−9\alpha\times10^{-9} m. The value of α\alpha is .
  9. PhysicsJEE Main 5 Apr 2026, Shift 1·Q14·MCQ·Easy–moderate
    Open
    In Young's double slit experiment, the fringe width of the interference pattern produced on the screen is 2.4 μm2.4\ \mu\mathrm{m}. If the experiment is carried out in another medium having refractive index 1.2, the fringe width will be μm\mu\mathrm{m}.
    1. (1)1.2
    2. (2)2
    3. (3)2.4
    4. (4)2.88
    We corrected a printing error in the original paper

    Source printed “the frings width of the interferences pattern”.

  10. PhysicsJEE Main 5 Apr 2026, Shift 2·Q17·MCQ·Moderate
    Open
    The 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 wavelength of light used. The intensity of the fringe, exactly opposite to one of the slits on the screen, placed at D=10 dD = 10\,d is
    1. (1)I04\dfrac{I_0}{4}
    2. (2)I02\dfrac{I_0}{2}
    3. (3)I0I_0
    4. (4)3I04\dfrac{3I_0}{4}
  11. PhysicsJEE Main 6 Apr 2026, Shift 1·Q11·MCQ·Easy–moderate
    Open
    In interference experiment the path difference between two interfering waves at a point A on the screen is λ/3\lambda/3, where λ\lambda is the wavelength of these waves, and at another point B the path difference is λ/6\lambda/6. The ratio of intensities at points A and B is .
    1. (1)3
    2. (2)4
    3. (3)1/3
    4. (4)1/4
  12. PhysicsJEE Main 6 Apr 2026, Shift 2·Q20·MCQ·Easy–moderate
    Open
    In 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, the distance between slits plane and screen is 50 cm, as shown in the figure below. If the resultant intensity at P is equal to the intensity due to individual slits, the minimum path difference between interfering waves is Å.
    1. (1)4000
    2. (2)3000
    3. (3)2000
    4. (4)1000
    We corrected a printing error in the original paper

    Source printed “the wavelength of incident of incident light”; “the separation between slits S1S_1 and 5 cm the distance”; “the path different” — corrected to the intended “the minimum path difference” (4000 Å, option (1), also gives the single-slit intensity; the key 2000 Å is the least).

Diffraction and polarisation

  1. PhysicsJEE Main 22 Jan 2026, Shift 2·Q15·MCQ·Easy–moderate
    Open
    Which of the following are true for a single slit diffraction?
    • (A)Width of central maxima increases with increase in wavelength keeping slit width constant.
    • (B)Width of central maxima increases with decrease in wavelength keeping slit width constant.
    • (C)Width of central maxima increases with decrease in slit width at constant wavelength.
    • (D)Width of central maxima increases with increase in slit width at constant wavelength.
    • (E)Brightness of central maxima increases for decrease in wavelength at constant slit width.
    1. (1)A, C, E only
    2. (2)A, D only
    3. (3)B, D only
    4. (4)B, C only
    We corrected a printing error in the original paper

    Source printed option (1) as “A, D, E only”; corrected to the intended “A, C, E only” (A, C, E are the true statements; as printed no option is correct).

  2. PhysicsJEE Main 23 Jan 2026, Shift 2·Q19·MCQ·Easy–moderate
    Open
    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∘\tan^{-1}(1.52) = 57.7^\circ, refractive indices of air and glass are 1.00 and 1.52, respectively)
    1. (1)39.6∘39.6^\circ
    2. (2)32.3∘32.3^\circ
    3. (3)42.6∘42.6^\circ
    4. (4)36.3∘36.3^\circ
  3. PhysicsJEE Main 24 Jan 2026, Shift 1·Q17·MCQ·Easy–moderate
    Open
    An unpolarised light is incident at an interface of two dielectric media having refractive indices of 2 (incident medium) and 232\sqrt3 (medium) respectively. To satisfy the condition that reflected and refracted rays are perpendicular to each other, the angle of incidence is .
    1. (1)60∘60^\circ
    2. (2)10∘10^\circ
    3. (3)30∘30^\circ
    4. (4)45∘45^\circ
  4. PhysicsJEE Main 2 Apr 2026, Shift 1·Q21·Numerical·Easy–moderate
    Open
    In single slit diffraction pattern, the wavelength of light used is 628 nm and slit width is 0.2 mm, the angular width of central maximum is α×10−2\alpha\times10^{-2} degrees. The value of α\alpha is .
  5. PhysicsJEE Main 4 Apr 2026, Shift 1·Q8·MCQ·Easy–moderate
    Open
    A slit of width aa is illuminated by light of wavelength λ\lambda. The linear separation between 1st1^{\text{st}} and 3rd3^{\text{rd}} minima in the diffraction pattern produced on a screen placed at a distance DD from the slit system is .
    1. (1)Dλa\dfrac{D\lambda}{a}
    2. (2)1.5Dλa1.5\dfrac{D\lambda}{a}
    3. (3)2Dλa2\dfrac{D\lambda}{a}
    4. (4)3Dλa3\dfrac{D\lambda}{a}
  6. PhysicsJEE Main 4 Apr 2026, Shift 1·Q20·MCQ·Moderate
    Open
    An unpolarized light is incident on the plane interface of air-dielectric medium shown in figure. If the incident angle is equal to Brewster angle, identify the expression representing reflected wave.
    1. (1)Eyj^sin⁡(kx−kz−ωt)E_y\hat j\sin(kx - kz - \omega t)
    2. (2)(Exi^+Ezk^)sin⁡(kx+ky−ωt)(E_x\hat i + E_z\hat k)\sin(kx + ky - \omega t)
    3. (3)(Eyj^+Ezk^)sin⁡(ky+kz−ωt)(E_y\hat j + E_z\hat k)\sin(ky + kz - \omega t)
    4. (4)(Exi^+Eyj^+Ezk^)sin⁡(kx+ky−kz−ωt)(E_x\hat i + E_y\hat j + E_z\hat k)\sin(kx + ky - kz - \omega t)
    We corrected a printing error in the original paper

    Source printed option (1) as “(Exi^+Eyj^)sin⁡(kx−kz−ωt)(E_x\hat i + E_y\hat j)\sin(kx - kz - \omega t)”; corrected to the intended “Eyj^sin⁡(kx−kz−ωt)E_y\hat j\sin(kx - kz - \omega t)” (at the Brewster angle the reflected light is polarised perpendicular to the plane of incidence xzxz, and an Exi^E_x\hat i component is not transverse to the reflected direction); source printed option (3) as “(Exj^+Eyk^)(E_x\hat j + E_y\hat k)”.

  7. PhysicsJEE Main 4 Apr 2026, Shift 2·Q17·MCQ·Easy–moderate
    Open
    An unpolarized light of certain intensity passes through a combination of two polarizers whose transmission axes are at 30∘30^\circ and 90∘90^\circ, respectively, with respect to the horizontal axis. A third polarizer with its transmission axis at 60∘60^\circ with the horizontal axis is placed between the two existing polarizers. The ratio of the output intensities with and without the third polarizer is .
    1. (1)3/4
    2. (2)4/3
    3. (3)9/4
    4. (4)4/9
  8. PhysicsJEE Main 6 Apr 2026, Shift 1·Q22·Numerical·Easy–moderate
    Open
    An unpolarized light of intensity I0I_0 passes through polarizer and then through a certain optically active solution and finally it goes to analyser. If the angle between analyser and polariser is 0∘0^\circ and intensity of light emerged from analyser is 38I0\dfrac38 I_0, the angle of rotation of the light by the solution with respect to analyser is degrees.
  9. PhysicsJEE Main 8 Apr 2026, Shift 2·Q22·Numerical·Easy–moderate
    Open
    Some distant star is to be observed by some telescope of diameter of objective lens a, at an angular resolution of 3.0×10−73.0\times10^{-7} radian. If the wavelength of light from the star reaching the telescope is 500 nm, the minimum diameter of the objective lens of the telescope is cm. (Nearest integer)
    We corrected a printing error in the original paper

    Source printed “Some distance star”.

Huygens principle

  1. PhysicsJEE Main 28 Jan 2026, Shift 1·Q16·MCQ·Easy–moderate
    Open

    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.

    In the light of the above statements, choose the correct answer from the options given below.

    1. (1)Both Statement-I and Statement-II are false.
    2. (2)Both Statement-I and Statement-II are true.
    3. (3)Statement-I is true but Statement-II is false.
    4. (4)Statement-I is false but Statement-II is true.