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1341
In YDS experiment, if the distance between the slits and also the distance between slits and screen is doubled, the fringe width:
A. Is halved
B. Remains the same
C. Becomes doubled
D. Becomes 4 times
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Correct Option
Explanation
Fringe width Δy = λL/d; doubling both L and d leaves their ratio unchanged, so fringe width remains the same.
1342
Newton's rings are experimentally derived from the phenomenon of
A. interference of light
B. diffraction of light
C. polarization of light
D. resolution of light
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Correct Option
Explanation
Newton's rings result from interference between light reflected from two surfaces with varying film thickness.
1343
For sustained interference we need two sources which emit radiations
A. having constant phase difference
B. with same intensity
C. in a narrow beam.
D. with same amplitude
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Correct Option
Explanation
Sustained (stable) interference requires a constant phase relationship (coherence) between the sources; equal intensity is not required.
1344
In a Young's double slit experiment, the fringe width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3 without disturbing the geometrical arrangement, the new fringe width will be
A. 0.3 mm
B. 0.53 mm
C. 540 microns
D. 0.4 mm
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Correct Option
Explanation
Fringe width ∝ wavelength; in water λ' = λ/n, so new width = 0.4 × (3/4) = 0.3 mm, option A.
1345
A Young's double slit set up for Interference is shifted from air to within water, then the fringe width
A. Increases
B. becomes Infinito
C. decreases
D. remains unchanged
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Correct Option
Explanation
Wavelength in water is reduced by refractive index, so fringe width β = Dλ/d decreases when immersed in water.
1346
The double slit experiment involves:
A. diffraction and interference.
B. diffraction only.
C. refraction.
D. diffraction and polarisation.
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Correct Option
Explanation
Young's double-slit experiment demonstrates interference effects arising from diffracted waves passing through the slits, so it involves diffraction and interference.
1347
The property of bending of light around an obstacle and spreading of light waves into geometric shadow of an obstacle is called:
A. Quantization of Light
B. Interference of Light
C. Polarization of Light
D. Diffraction of Light
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Correct Option
Explanation
Diffraction is the bending and spreading of waves around obstacles and into regions that would be shadowed geometrically.
1348
When a thin transparent plate of thickness t and refractive index μ is placed in the path of one of the two interfering waves of light, then the path difference changes by
A. −(μ − 1) / t
B. (μ + 1) t
C. (μ − 1) t
D. (μ + 1) λ
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Correct Option
Explanation
A plate of index μ and thickness t introduces an additional optical path (μ − 1)t compared to the same thickness of air.
1349
Phase change of 180° is equivalent to a path difference of:
A. λ/2
B. 2λ
C. λ/4
D. λ
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Correct Option
Explanation
The explanatory answer in the block states that 180° corresponds to λ/2, so option C is correct.
1350
A source X of unknown frequency produces 8 beats with a source of 250 Hz and 12 beats with a source of 270 Hz. The frequency of source X is
A. 258 Hz
B. 242 Hz
C. 282 Hz
D. 262 Hz
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Correct Option
Explanation
|fX−250|=8 ⇒ fX=258 or 242; |fX−270|=12 ⇒ fX=258 or 282, intersection is 258 Hz.
