Typical heights of atmospheric/ionospheric regions used in radio propagation: match layers to representative altitudes. List I (Layer) A. D layer B. E layer C. F layer D. Troposphere List II (Approximate height) 110 km 10 km 60 km 350 km
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AA-3, B-1, C-4, D-2
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BA-2, B-1, C-4, D-2
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CA-3, B-2, C-1, D-4
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DA-4, B-3, C-1, D-2
Answer
Correct Answer: A-3, B-1, C-4, D-2
Explanation
Introduction / Context:Radio systems exploit the troposphere and ionosphere differently. Recognizing the approximate heights of D, E, and F layers and the troposphere helps explain skip distance, absorption, and refraction phenomena in HF/VHF links.
Given Data / Assumptions:
- D layer: lowest ionospheric region, strongest daytime absorption.
- E layer: mid ionospheric region enabling short-hop refraction.
- F layer: highest ionospheric region (often F1 and F2), supports long-distance HF propagation.
- Troposphere: weather region, significant for troposcatter and ducting around ~10–12 km.
Concept / Approach:
Use representative altitudes commonly cited in exam contexts: D ≈ 60 km, E ≈ 110 km, F ≈ 350 km (upper F2 nighttime value), troposphere ≈ 10 km (tropopause vicinity). Exact values vary with time of day, season, and solar activity, but these anchors are standard.
Step-by-Step Solution:
D layer → ~60 km ⇒ A-3.E layer → ~110 km ⇒ B-1.F layer → ~350 km ⇒ C-4.Troposphere → ~10 km ⇒ D-2.Verification / Alternative check:
Propagation handbooks tabulate similar nominal heights. Practical HF planning tools also model variable E/F heights around these figures, confirming the mapping.
Why Other Options Are Wrong:
- Swapping D and E heights misrepresents absorption and skip effects.
- Placing the troposphere at 60–350 km confuses neutral atmosphere with ionospheric plasma regions.
Common Pitfalls:
Assuming fixed heights; in reality, the F layer splits (F1, F2) in the day and merges at night, and altitudes shift with solar conditions. Exams typically expect the representative figures used here.
Final Answer:
A-3, B-1, C-4, D-2