MCQ on Radio Wave Propagation

Radio propagation is never completely foreseeable, strong probability notions are used while broadcasting. Over the course of a century, several protocols for the transmission of radio waves have been suggested and established and the mode chosen is highly dependent on the distance between the transmitter and the receiver. Objects along their route and the medium through which they travel have a significant impact on radio waves. This implies that the transmission of radio signals is important when developing or running a radio system. The intensity and quality of the received signal are determined by the property of the route along which the radio signal travels.

1. What frequency is ground wave propagation employed up to?

a) 2MHz

b) 2GHz

c) 30MHz

d) 30GHz 

Answer- a

Explanation: Up to 2MHz, ground wave propagation, also known as surface wave propagation, is employed. At 2MHz to 30MHz, sky wave propagation is employed.

2. Which component of the electric field in a ground wave propagation gets short circuited when it comes into touch with the earth?

a) Horizontal

b) Vertical

c) Both horizontal and vertical

d) Neither horizontal nor vertical

Answer- a

Explanation: Earth short circuits every horizontal component of an electric field that comes into touch with it. Vertical antennas are used to propagate ground waves; hence they are vertically polarized.

3. The earth acts like a _________ during ground wave propagation.

a) Leaky capacitor

b) Leaky Inductor

c) Series combination of capacitor and inductor

d) Parallel combination of capacitor and inductor 

Answer- a 

Explanation: Earth short circuits every horizontal component of an electric field that comes into touch with it. As a result, the earth acts as though it has a leaking capacity. In a shunt with a capacitor, it creates a resistor.

4. The frequencies __________ are reflected in sky wave propagation.

a) 2MHz

b) 2 MHz to 30MHz

c) 2 GHz to 30 GHz

d) 30 GHz to 50GHz 

Answer- b

Explanation: Up to 2MHz, ground wave propagation, also known as surface wave propagation, is employed. At 2MHz to 30MHz, sky wave propagation is employed.

5. How far out from the earth’s surface can sky waves propagate?

a) 50 to 400km

b) Below 50 km

c) 600 to 750km

d) 50 to 400 m 

Answer- a

Explanation: Ionosphere propagation, also known as sky wave propagation, reflects waves with frequencies ranging from 2 to 30 MHz. It may be found at distances of 50 to 400 kilometres from the Earth’s surface.

 6. Waves with frequencies of ________ are reflected by space wave propagation.

a) Below 2 GHz

b) 2 to 30MHz

c) Above 30GHz

d) Above 30MHz

Answer- d

Explanation: Up to 2MHz, ground wave propagation, sometimes called surface wave propagation, is employed. At 2MHz to 30MHz, sky wave propagation is employed. Frequencies exceeding 30MHz are reflected by space wave propagation.

7. What frequency band does a space wave propagate in?

a) VHF

b) HF

c) MF

d) EHF

Answer- a 

Explanation: Frequencies in the 30 to 300 MHz range are reflected by space wave propagation. As a result, it propagates on the VHF frequency.

300 KHz – 3MHz MF

30GHz-300GHz EHF

8. The height of the antenna may be reduced to enhance LOS communication.

a) True

b) False

Answer- b

Explanation: Line of sight is a direct communication connection between the transmitter and the receiver. When the antenna height is raised, the LOS improves as well.

9. Which of the following modes of propagation is used to guide waves over the earth’s surface?

a) Ground wave

b) Sky wave

c) LOS

d) Space wave 

Answer- a 

Explanation: The waves are steered along the earth’s surface in ground wave or surface wave propagation. They are reflected at various levels of the ionosphere as sky waves. The direct or indirect way of transmission from transmitter to receiver is used in space waves.

10. The ionosphere functions as a reflecting surface for the waves in which of the following modes of propagation?

a) Ground wave

b) Sky wave

c) Space wave

d) LOS 

Answer- b 

Explanation: In sky wave or ionospheric wave propagation, various frequencies of waves are reflected from the ionosphere layers.

11. What is the wavelength of Super high frequency (SHF), which is utilized mostly in radar and satellite communication? 

a) 1 m -10 m

b) 1 cm -10 cm

c) 10 cm -1 m

d) 0.1 cm -1 cm

Answer- b

12. Which of the following is a high-frequency application?

a) SONAR

b) Subsurface communication

c) Radio navigation

d) Facsimile

Answer- d

13. A wavefront is a collection of points that acquire comparable-

a) Phase

b) Frequency

c) Amplitude

d) Wave equation

Answer- a

14. How is phase velocity determined in which kind of waveform?

a) Sinusoidal

b) Rectangular

c) Square

d) Triangular

Answer- a, as it creates a sine wave when date points are entered to create a wave.

 15. In free space, which of the following is/are not present?

a) Solid bodies

b) Ionized particles

c) Interference of normal radiation & radio wave propagation

d) All of the above

Answer- d

16. The fundamental definition of power density is _______ power per unit area.

a) Reflected

b) Refracted

c) Radiated

d) Diffracted

Answer- c

17. What is the phase difference between two waves with the same source going by separate ways to reach at the same place if their path difference is /2?

a) β x (λ/2)

b) β / (λ/4)

c) β + (λ/5)

d) β – (λ/2)

Answer- a

18. Which ionization layer is present throughout the day but disappears at night owing to the greatest recombination rate?

a) D-region

b) Normal E-region

c) Sporadic E-region

d) Appleton region

Answer- a

 19. What is the height range in which an occasional E-region may occur in comparison to a typical E-region?

a) 20 km – 25km

b) 45 km – 95 km

c) 90 km – 130 km

d) 140 km – 300 km

Answer- c, as height is important for these waves to have seamless propagation

20. For ____ frequency radio waves, the F2 layer of the Appleton area operates as a strong reflecting medium.

a) Low

b) Moderate

c) High

d) All of the above

Answer- c

21. Which of the following parameters is required to derive the time-varying electromagnetic field?

a) Electric field intensity

b) Magnetic field intensity

c) Current density

d) Power density

Answer- c

22. What is an antenna ?

a) Impedance matching device

b) Sensor of electromagnetic waves

c) Transducer between guided wave & free space wave

d) Receiving radio waves

Answer- d