Choose the correct statements about waves and phase: definitions of a wavefront, a plane wave, and the importance of relative phase between waves.

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