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

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:

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