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1481
The distance between different interference fringes is:
A. Variable
B. Same
C. Different
D. None of these
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Correct Option
Explanation
In a given interference setup with fixed geometry and wavelength, fringe spacing is constant so the distance between adjacent fringes is the same.
1482
In YDS experiment, fringe spacing means the distance between two consecutive fringes.
A. Bright
B. Dark
C. Any of A or B
D. None of these
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Correct Option
Explanation
Fringe spacing refers to the distance between any two consecutive fringes, whether bright or dark.
1483
8. Huyghen's principle of secondary waves
A. is a geometrical method to find the position of a wavefront
B. is used to determine the velocity of light
C. gives us the magnifying power of a microscope
D. allows us to find the focal length of a thick lens
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Correct Option
Explanation
Huygens' principle is a constructive geometrical method for locating wavefront positions by secondary wavelets.
1484
A thin wedge-shaped air film is trapped between two glass plates, and a parallel beam of monochromatic light is incident normally on it. The fringes observed are
A. of irregular shape
B. hyperbolic
C. circular
D. straight
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Correct Option
Explanation
A linear wedge produces fringes of equal thickness which appear as straight, parallel fringes.
1485
A slit of width 0.15 cm is illuminated by light of wavelength 5 × 10^-5 cm and the diffraction pattern is obtained at a distance 2.1 m. The width of central fringe is
A. 0.42 cm
B. 0.56 cm
C. 0.14 cm
D. 0.28 cm
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Correct Option
Explanation
Central width = 2Dλ/a = 2×2.1×5e-7 / 1.5e-3 ≈ 1.4e-3 m = 0.14 cm, so option A.
1486
The displacement of interfering light waves are y1 = 4 sin ωt and y2 = 3 sin(ωt + 1/2). What is the amplitude of the resultant waves?
A. 1
B. 5
C. zeń
D. 7
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Correct Option
Explanation
Resultant amplitude = sqrt(A1^2 + A2^2 + 2A1A2 cos φ) = sqrt(16+9+24 cos0.5) ≈ 6.79 ≈ 7, so option B.
1487
For bright fringe formation, the path difference is:
A. (2n + 1)λ/2 where n = 0,1,2,...
B. (? garbled) n+? where n = 0,1,2,...
C. nλ where n = 0,1,2,...
D. n+1
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Correct Option
Explanation
Bright fringes occur at constructive interference where path difference equals nλ (n = 0,1,2,...), so option B is correct.
1488
A grating has 5000 lines per centimeter. Then grating element will be given as:
A. 2 × 10^4 m
B. 2 × 10^-10 m
C. 2 × 10^3 m
D. 2 × 10^-6 m
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Correct Option
Explanation
5000 lines/cm = 5×10^5 lines/m, so spacing a = 1/(5×10^5) m = 2×10^-6 m.
1489
In Young's double slit experiment using sodium light (λ = 5898 Å), 92 fringes are seen. If a given colour (λ = 5461 Å) is used, how many fringes will be seen?
A. 62
B. 67
C. 85
D. 99
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Correct Option
Explanation
Number of fringes ∝ 1/λ, so N2 = 92×(5898/5461) ≈ 99 fringes.
1490
In 1912, Laue suggested that a crystal can serve as a grating for X-ray diffraction.
A. Three dimensional
B. Zero dimensional
C. Two dimensional
D. One-dimensional
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Correct Option
Explanation
Laue proposed that the three-dimensional periodic lattice of a crystal acts as a diffraction grating for X-rays.
