Diffraction (due to a single slit, width of central maximum ) NEET Questions

Physics - Optics

Diffraction (due to a single slit, width of central maximum ) MCQ Questions


7.
The ANGULAR WIDTH of the central maximum in single-slit diffraction is:
A.
θ₁ = λ/a (this is only the half-angular width, not the full width)
B.
2θ₁ = λ/(2a)
C.
2θ₁ = 2 sin⁻¹(λ/a) ≈ 2λ/a (for small angles), where the first minima occur at ±θ₁
D.
2θ₁ = 4λ/a
😑 View Answer Rough Work Error
ANSWER :
C. 2θ₁ = 2 sin⁻¹(λ/a) ≈ 2λ/a (for small angles), where the first minima occur at ±θ₁
8.
The LINEAR WIDTH of the central maximum on a screen at distance D from the slit is:
A.
W = 4λD/a
B.
W = λD/(2a)
C.
W = 2λD/a (twice the distance from centre to the first minimum)
D.
W = λD/a (this is the distance to the FIRST minimum, not the full central maximum width)
😑 View Answer Rough Work Error
ANSWER :
C. W = 2λD/a (twice the distance from centre to the first minimum)
9.
If the slit width in a single-slit diffraction experiment is HALVED (a → a/2) while wavelength and screen distance remain constant, the width of the central maximum:
A.
Remains unchanged
B.
Halves (W ∝ a)
C.
Becomes four times (W ∝ 1/a²)
D.
Doubles (W = 2λD/a → W' = 2λD/(a/2) = 4λD/a = 2W)
😑 View Answer Rough Work Error
ANSWER :
D. Doubles (W = 2λD/a → W' = 2λD/(a/2) = 4λD/a = 2W)
10.
In a single-slit diffraction experiment with slit width a = 0.1 mm, wavelength λ = 500 nm, and screen at D = 1 m, the width of the central maximum is:
A.
0.5 cm (this is only the half-width y₁)
B.
5 mm
C.
2 cm
D.
1 cm (W = 2λD/a = 2 × 500×10⁻⁹ × 1 / 0.1×10⁻³ = 2 × 500×10⁻⁹/(10⁻⁴) = 10⁻² m = 1 cm)
😑 View Answer Rough Work Error
ANSWER :
D. 1 cm (W = 2λD/a = 2 × 500×10⁻⁹ × 1 / 0.1×10⁻³ = 2 × 500×10⁻⁹/(10⁻⁴) = 10⁻² m = 1 cm)
11.
If wavelength is DOUBLED (λ → 2λ) in a single-slit diffraction experiment, the width of the central maximum:
A.
Remains the same
B.
Quadruples
C.
Halves
D.
Doubles (W = 2λD/a → W' = 2(2λ)D/a = 2W)
😑 View Answer Rough Work Error
ANSWER :
D. Doubles (W = 2λD/a → W' = 2(2λ)D/a = 2W)
12.
If screen distance is TRIPLED (D → 3D) in a single-slit diffraction experiment, the width of the central maximum:
A.
Remains the same
B.
Becomes 9 times
C.
Increases by √3
D.
Triples (W = 2λD/a → W' = 2λ(3D)/a = 3W)
😑 View Answer Rough Work Error
ANSWER :
D. Triples (W = 2λD/a → W' = 2λ(3D)/a = 3W)