Choose the correct statements about waves and phase: definitions of a wavefront, a plane wave, and the importance of relative phase between waves.
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AA wavefront is the surface formed by the locus of points that share the same phase.
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BA wave whose surfaces of constant phase are parallel planes is called a plane wave.
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CIn interference and propagation, relative phase between waves matters more than the absolute phase at a single point.
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DAll of these
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EOnly (a) and (b)
Answer
Correct Answer: All of these
Explanation
Introduction / Context:Wave theory underpins optics, radar, acoustics, and remote sensing. Understanding wavefronts, plane waves, and phase relationships enables interpretation of coherence, interference, and imaging performance.
Given Data / Assumptions:
- Monochromatic waves are considered for simplicity.
- Phase is defined modulo 2π and can be mapped across space.
- Media are assumed homogeneous for the plane-wave concept.
Concept / Approach:A wavefront connects points of equal phase, such as crests in a harmonic wave. If these wavefronts are planar and equally spaced, the wave is a plane wave, an idealization widely used in analysis. Interference patterns depend on phase differences between waves; shifting both waves by the same absolute phase does not alter measurable outcomes, hence the primacy of relative phase.
Step-by-Step Solution:Confirm definition of wavefront as constant-phase surface.Identify plane waves by parallel plane wavefronts.Recognize interference depends on phase difference, not absolute phase.Therefore, all statements are correct, so choose “All of these.”
Verification / Alternative check:Huygens–Fresnel principle and Fourier optics rely on wavefront concepts; interferometry (including SAR) measures relative phase to infer geometry.
Why Other Options Are Wrong:
- Limiting correctness to only two statements ignores the central role of relative phase in interference.
Common Pitfalls:Confusing rays (energy flow directions) with wavefronts (phase surfaces); over-interpreting absolute phase which is typically unobservable.
Final Answer:All of these