In Young’s double-slit experiment, the two slits act as coherent sources of equal amplitude A and wavelength λ. In another experiment with the same set up, the two slits are of equal amplitude A and wavelength λ but are incoherent. The ratio of the intensity of light at the mid-point of the screen in the first case to that in the second case is:

(1) 1 : 2

(2) 2 : 1

(3) 4 : 1

(4) 1 : 1

Subtopic:  Young's Double Slit Experiment |
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A monochromatic beam of light falls on the YDSE apparatus at some angle (say θ) as shown in the figure. A thin sheet of glass is inserted in front of the lower slit S2. The central bright fringe (path difference = 0) will be obtained:

(1) At O

(2) Above O

(3) Below O

(4) Anywhere depending on angle θ, the thickness of plate t and refractive index of glass μ

Subtopic:  Young's Double Slit Experiment |
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Two ideal slits S1 and S2 are at a distance d apart and illuminated by the light of wavelength λ passing through an ideal source slit S placed on the line through S2 as shown. The distance between the planes of slits and the source slit is D. A screen is held at a distance D from the plane of the slits. The minimum value of d for which there is darkness at O is:

(1) 3λD2

(2) λD

(3) λD2

(4) 3λD

Subtopic:  Young's Double Slit Experiment |
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Two point sources X and Y emit waves of same frequency and speed but Y lags in phase behind X by 2πl radian. If there is a maximum in direction D the distance XO using n as an integer is given by

(1) λ2(nl)

(2) λ(n+l)

(3) λ2(n+l)

(4) λ(nl)

Subtopic:  Diffraction |
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A beam with wavelength λ falls on a stack of partially reflecting planes with separation d. The angle θ that the beam should make with the planes so that the beams reflected from successive planes may interfere constructively is (where n =1, 2, ……)

(1) sin1nλd

(2) tan1nλd

(3) sin1nλ2d

(4) cos1nλ2d

Subtopic:  Interference vs Diffraction |
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Two coherent sources separated by distance \(d\) are radiating in a phase having wavelength \(\lambda.\) A detector moves in a big circle around the two sources in the plane of the two sources. The angular position of \(n=4\) interference maxima is given as:

  
1. \(sin^{-1}\frac{n\lambda}{d}\)
2. \(cos^{-1}\frac{4\lambda}{d}\)
3. \(tan^{-1}\frac{d}{4\lambda}\)
4. \(cos^{-1}\frac{\lambda}{4d}\)

Subtopic:  Interference vs Diffraction |
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In a single slit diffraction of light of wavelength λ by a slit of width e, the size of the central maximum on a screen at a distance b is

(1) 2bλ+e

(2) 2bλe

(3) 2bλe+e

(4) 2bλee

Subtopic:  Diffraction |
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In a YDSE bi-chromatic light of wavelengths, 400 nm and 560 nm are used. The distance between the slits is 0.1 mm and the distance between the plane of the slits and the screen is 1 m. The minimum distance between two successive regions of complete darkness is: 

(1) 4 mm

(2) 5.6 mm

(3) 14 mm

(4) 28 mm

Subtopic:  Young's Double Slit Experiment |
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In Young's double-slit experiment, the intensity at a point is (1/4) of the maximum intensity. The angular position of this point is:

(1) sin-1(λ/d)

(2) sin-1(λ/2d)

(3) sin-1(λ/3d)

(4) sin-1(λ/4d)

Subtopic:  Young's Double Slit Experiment |
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A beam of electron is used in a YDSE experiment. The slit width is d. When the velocity of the electron is increased, then,

(1) No interference is observed

(2) Fringe width increases

(3) Fringe width decreases

(4) Fringe width remains the same

Subtopic:  Young's Double Slit Experiment |
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