Interference (Young's double-slit experiment and expression for fringe width, coherent sources,..) NEET Questions

Physics - Optics

Interference (Young's double-slit experiment and expression for fringe width, coherent sources,..) MCQ Questions


13.
For sustained interference, the necessary conditions are:
A.
Maximum intensity and minimum frequency
B.
Different wavelengths and amplitudes
C.
Sources must be perfectly aligned
D.
Coherent sources (same frequency, constant phase difference) and approximately equal amplitudes
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ANSWER :
D. Coherent sources (same frequency, constant phase difference) and approximately equal amplitudes
14.
Why are two sources obtained from the SAME source through a divider (like double slit) coherent, while two SEPARATE light bulbs are not?
A.
Sources from the same primary source share phase fluctuations (they're 'locked' in phase); separate sources have independent random fluctuations
B.
Because separate sources have different wavelengths
C.
Because the same source has more energy
D.
It's a coincidence
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ANSWER :
A. Sources from the same primary source share phase fluctuations (they're 'locked' in phase); separate sources have independent random fluctuations
15.
Young's double-slit experiment was first performed by Thomas Young in:
A.
1905
B.
1801
C.
1678
D.
1864
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ANSWER :
B. 1801
16.
In Young's double-slit experiment, what is the role of the first single slit S placed before the double slits S₁ and S₂?
A.
It diffracts the light
B.
It splits white light into colors
C.
It produces a coherent monochromatic source that illuminates both S₁ and S₂ identically, ensuring they act as coherent sources
D.
It prevents background light from reaching the screen
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ANSWER :
C. It produces a coherent monochromatic source that illuminates both S₁ and S₂ identically, ensuring they act as coherent sources
17.
In Young's double-slit experiment, the path difference (S₂P - S₁P) at a point P on the screen at distance x from the centre is approximately (assuming D >> d, x):
A.
d²/D
B.
xD/d
C.
xd/D, where d is slit separation and D is the slit-to-screen distance
D.
x²/D
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ANSWER :
C. xd/D, where d is slit separation and D is the slit-to-screen distance
18.
In Young's double-slit experiment, the condition for the n-th bright fringe at distance x_n from central maximum is:
A.
x_n = (n + 1/2)λD/d
B.
x_n = D/(nλd)
C.
x_n = nλd/D
D.
x_n = nλD/d
😑 View Answer Rough Work Error
ANSWER :
D. x_n = nλD/d