Question

VHF waves travel as _______.

• A. surface waves
• B. ground waves
• C. sky waves
• D. space waves

Hint:

VHF waves can’t bend or reflect well — they travel in straight lines and need clear paths, so they are called space waves.

Answer 1

The Correct Option is D

Step 1: Frequency range of VHF
VHF (Very High Frequency) spans from 30 MHz to 300 MHz. Common examples include FM radio, TV broadcasts, and two-way radios.

Step 2: Types of wave propagation
- Surface/Ground waves: Follow the Earth's surface; dominate at lower frequencies (below 2 MHz).
- Sky waves: Reflect off the ionosphere; efficient in HF band (3–30 MHz).
- Space waves: Travel in straight lines (LOS); used by VHF, UHF, and higher frequencies.

Step 3: Why VHF uses space waves
VHF signals:
- Do not reflect efficiently off the ionosphere.
- Do not bend around obstacles well.
- Are absorbed quickly when obstructed.
Hence, they rely on line-of-sight (LOS) propagation between transmitter and receiver — a space wave phenomenon.

Step 4: Practical implication
This is why VHF communication towers are kept tall, and why communication is lost beyond the visual horizon.

Conclusion: VHF signals travel primarily as space waves.