Introduction to Radio Wave Propagation

Instructions

This quiz contains 20 multiple-choice questions. Each question has exactly one correct answer.
Questions are restricted to the first three levels of Bloom's taxonomy: Remembering, Understanding, and Applying.
Attempt all questions before submitting.
Click Submit Quiz to view your score, the correct answers, and detailed explanations.
Each question carries 1 mark. Total: 20 marks. Suggested time: 30 minutes.

Bloom's levels covered: Level 1 — Remember Level 2 — Understand Level 3 — Apply

Part A: Quiz Questions

1. Which of the following is the standard designator for radio waves in the electromagnetic spectrum?Remember

a) Visible light b) Radio frequency (RF) waves c) X-rays d) Gamma rays

2. What is the approximate frequency range of radio waves?Remember

a) 20 Hz – 20 kHz b) 430 – 770 THz c) 3 kHz – 300 GHz d) Above 300 GHz

3. Which are the three principal mechanisms of radio wave propagation?Remember

a) Ground wave, sky wave, and line-of-sight (space wave) b) Reflection, diffraction, and absorption c) Scattering, refraction, and attenuation d) Transmission, reception, and modulation

4. Which layer of the ionosphere is primarily responsible for reflecting medium-frequency (MF) and high-frequency (HF) sky waves back to Earth during the day?Understand

a) The troposphere b) The F layer (F1/F2) c) The ozone layer d) The stratosphere

5. The bending of a radio wave as it passes from one medium into another of different density is called:Remember

a) Diffraction b) Scattering c) Reflection d) Refraction

6. A radio transmitter operates at 150 MHz. What is its wavelength in free space?Apply

a) 2.0 m b) 0.5 m c) 1.5 m d) 4.5 m

7. Ground wave propagation is most effective for which frequency range?Understand

a) VHF and above (30–300 MHz and higher) b) Microwave frequencies c) Very low to medium frequencies (VLF – MF, up to about 2 MHz) d) Optical frequencies

8. A point-to-point microwave link at 6 GHz with adequate antenna heights has a clear path between antennas. Which propagation mechanism supports this link?Apply

a) Ground (surface) wave b) Line-of-sight (space wave) c) Ionospheric sky wave d) Tidal wave

9. The reduction in signal strength as a radio wave travels through a medium is known as:Remember

a) Modulation b) Multiplexing c) Attenuation d) Amplification

10. The maximum sky-wave propagation distance on Earth is approximately:Understand

a) 4,000 km (one ionospheric hop) b) 40,000 km c) 400 km d) Unlimited, since waves never fade

11. In free space, radio signal power decreases with distance d according to which law?Remember

a) Inverse distance law (1/d) b) Inverse square law (1/d²) c) Inverse cube law (1/d³) d) Exponential law (e^d)

12. An FM broadcast station at 100 MHz in Nairobi relies mainly on which propagation mode to serve listeners within about 50–80 km?Apply

a) Ionospheric sky wave b) Ground (surface) wave c) Earth–ionosphere waveguide mode d) Line-of-sight (space wave)

13. Diffraction of radio waves is best described as:Understand

a) The bouncing of waves off the Earth's surface b) The conversion of wave energy into heat c) The bending of waves around obstacles and over sharp edges d) The splitting of a wave into multiple frequencies

14. Which frequency band is typically used for ionospheric (sky wave) long-distance communication?Understand

a) HF (3–30 MHz) b) VHF (30–300 MHz) c) UHF (300 MHz–3 GHz) d) SHF (3–30 GHz)

15. The effective Earth radius used in propagation modelling (k × R, where R ≈ 6,371 km) is typically taken as about 8,500 km. What value of effective Earth radius factor k does this correspond to?Apply

a) k = 1 b) k = 4/3 c) k = 2 d) k = 1/2

16. The phenomenon by which a radio wave changes direction as it passes through the ionosphere is caused by:Understand

a) Absorption by water vapour b) Scattering by rain droplets c) A gradual change in the refractive index with ionisation density and height d) Reflection from mountain peaks

17. The region around a transmitting antenna where the electric and magnetic fields are stored and do not contribute to radiation is called the:Remember

a) Fraunhofer (far-field) region b) Radiation zone c) Tropospheric duct d) Reactive near-field region

18. A signal of 10 mW suffers a path loss such that the received power is 10 μW. What is the path loss in decibels?Apply

a) 30 dB b) 20 dB c) 60 dB d) 40 dB

19. Fading caused by multiple propagation paths (direct, reflected, diffracted) arriving at the receiver with different phases is called:Remember

a) Thermal fading b) Multipath fading c) Absorptive fading d) Polarisation fading

20. A VHF signal at 150 MHz propagates beyond the geometric horizon because the radio horizon is longer than the optical horizon, mainly due to:Apply

a) Ionospheric absorption b) Magnetic field effects on electrons c) Refraction of radio waves toward the Earth in the troposphere d) Reflection from the stratosphere

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Instructions

Part A: Quiz Questions

Your Score

Part B: Post-Test Answer Key & Explanations