As shown in the figure, which is the correct label for the Fresnel area? (Multiple choice)

Question

Exhibit

Options

• Aa
• Bb
• Cc
• Dd

• A
  77% (34)
• B
  7% (3)
• D
  16% (7)

Explanation

Fresnel zones are numbered sequentially from the innermost region outward, with Zone 1 being the central ellipsoidal region closest to the line-of-sight path, and each successive zone adding a half-wavelength (λ/2) of extra path length. Options A and C correctly label zones according to this inside-out convention, placing lower zone numbers at the center and higher numbers toward the periphery.

Options B and D are incorrect because they likely reverse the numbering order (labeling outer rings with smaller numbers) or misplace zone boundaries - both common errors that violate the fundamental definition where the nth Fresnel zone has a path difference of nλ/2 from the direct path.

Memory tip: Think "Fresnel = First in the middle" - Zone 1 is always the central bullseye, and you count outward like rings on a target. If the smallest number isn't at the center, the label is wrong.

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