NEET Physics: Diffraction Practice Questions
14 free multiple-choice questions on Diffraction (Wave Optics) for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more NEET questions in the app →Q1. When light passes through a narrow slit, the resulting pattern exhibits alternating regions of bright and dark fringes. This pattern is an example of:
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Correct answer: C — Diffraction
The pattern formed by the spreading of light waves as they diffract around an aperture is known as diffraction.
Q2. In single-slit diffraction, the angular positions of the minima are determined by which relationship?
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Correct answer: D — sinθ = nλ/a
For single-slit diffraction, the condition for minima (destructive interference) is given by a relationship involving the wavelength (λ), the slit width (a), and the angle (θ): a sinθ = nλ, where n is an integer (1, 2, 3...).
Q3. The fringe width in a diffraction pattern is primarily determined by which geometric factor of the setup?
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Correct answer: C — The width of the slit
The angular spread and thus the width of the diffraction fringes are directly determined by the physical width of the aperture (slit width) through which the waves pass.
Q4. For a plane wave incident on a screen, the intensity of the diffracted light is distributed in a pattern that is generally:
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Correct answer: A — Concentrated near the center
Diffraction results in a spreading of light, leading to an intensity distribution where the intensity is generally highest at the center and gradually decreases as the angle increases.
Q5. Which principle forms the basis for understanding the phenomenon of diffraction of light?
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Correct answer: C — Huygens' principle
Diffraction is fundamentally explained by Huygens' principle, which states that every point on a wavefront acts as a source of secondary spherical wavelets, and the new wavefront is the envelope of these wavelets.
Q6. The angular spread of a diffraction pattern is primarily dependent on which of the following parameters?
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Correct answer: B — Wavelength of the light
The angular width of the diffraction pattern is inversely related to the wavelength of the light (θ∝ λ/a), meaning shorter wavelengths lead to a wider pattern spread for a fixed slit width.
Q7. In a diffraction grating, if the wavelength of light is doubled, how does the angular separation between the maxima change, assuming the grating spacing remains constant?
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Correct answer: A — It is doubled
The angular separation (θ) for constructive interference depends on the grating spacing (d) and the wavelength (λ). Since sin θ= mλ/d, doubling λ doubles the angle θ for a fixed order m.
Q8. The condition for destructive interference in two-source interference (like in a double-slit setup) is achieved when the path difference is equal to an odd multiple of half the wavelength. What is the path difference for the first minimum?
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Correct answer: A — λ/2
For the first minimum (destructive interference), the path difference must be exactly half a wavelength, i.e., dsin θ= λ/2.
Q9. If the wavelength of the light used in a diffraction experiment is doubled, how does the angular width of the diffraction pattern change (assuming fixed slit width)?
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Correct answer: D — It is doubled
Since the angular width is proportional to the wavelength (θ∝ λ), doubling the wavelength will double the angular width of the diffraction pattern.
Q10. In a double-slit experiment, the interference pattern is formed due to the superposition of waves. If the path difference between the waves arriving at a point is zero, the resultant intensity will be:
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Correct answer: D — Maximum
When the path difference is zero (constructive interference), the waves are in phase, leading to maximum intensity.
Q11. Which principle is fundamental to understanding the phenomenon of diffraction?
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Correct answer: A — Huygens' principle
Huygens' principle states that every point on a wavefront acts as a source of secondary spherical wavelets, which is the foundation for explaining diffraction and interference.
Q12. For single-slit diffraction, the intensity of the central maximum is maximum at which angle?
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Correct answer: C — θ= 0 radians
The intensity is maximum at the central angle, which corresponds to θ= 0 (or the angle corresponding to the central maximum).
Q13. When light passes through a narrow aperture, the resulting pattern arises due to which effect?
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Correct answer: C — Diffraction
Diffraction is the bending or spreading of waves as they pass through an aperture or around an obstacle, which is the core mechanism for patterns observed in diffraction experiments.
Q14. If the wavelength of light is doubled, how will the angular width of the diffraction pattern change, assuming the slit width remains constant?
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Correct answer: D — It will be doubled
The width of the diffraction pattern is inversely proportional to the wavelength (Δθ∝ 1/λ). If λ doubles, the angular width of the pattern will be halved (or the pattern spreads out, depending on the exact context, but the angular spread calculation relates directly to λ). Since the condition sin(θ) = nλ must hold, if λ doubles, the angle for a fixed n must increase for the pattern to fit, meaning the pattern spreads out, proportional to λ. (A simpler conceptual interpretation for easy level is that the fringe width relation dictates Δx ∝ λ or Δθ∝ λ for fixed geometry).
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