# MCQ in Radiation and Wave Propagation Part 5 | ECE Board Exam

(Last Updated On: May 3, 2020) This is the Multiples Choice Questions Part 5 of the Series in Radiation and Wave Propagation as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

#### MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Wave Propagation
• MCQ in Wavelength Calculations
• MCQ in Diversity Systems

#### Continue Practice Exam Test Questions Part 5 of the Series

201. The cumulative sum of the direct, ground-reflected, and surface waves is reflected to as _________.

a. Space wave

b. Ground wave

c. Sky wave

d. Direct waves

Solution:

202. The D layer of the ionosphere reflects _________ waves.

a. MF and HF

b. VLF and MF

c. MF and VHF

d. VLF and LF

Solution:

203. A diversity scheme wherein the same radio signal is repeated or transmitted more than once.

a. polarization diversity

b. field component diversity

c. time diversity

d. frequency diversity

Solution:

204. The disadvantage of ground wave propagation is

a. Ground waves require a relatively high transmission power

b. Ground waves are limited to very low, low and medium frequencies requiring large antennas

c. Ground losses very considerably with surface material

d. Any of these

Solution:

205. A range of microwave frequencies more easily passed by the atmosphere than the others is called a

a. window

b. critical frequency

c. gyro frequency range

d. resonance in the atmosphere

Solution:

206. It is simply the orientation of the electric field vector in respect to the surface of the Earth

a. Polarization

b. Wavefront

c. Rays

d. Power density

Solution:

207. For an isotropic antenna radiating 100W of power, what is power density 1000m from the source?

a. 1.99 µW/m^2

b. 7.96 µW/m^2

c. 3.22 µW/m^2

d. 9.17 µW/m^2

Solution:

208. The ground wave eventually disappears, as moves away from the transmitter, because of

a. interference from the sky wave

b. loss of line-of-sight conditions

c. maximum single hop distance limitations

d. tilting

Solution:

209. If the electric field is propagating parallel to the surface of the Earth, the polarization is _________.

a. Circular

b. Vertical

c. Horizontal

d. Elliptical

Solution:

210. A taxi company uses a central dispatcher, with an antenna at the top of a 15m tower, to communicate with taxi cabs. The taxi antennas are on the roofs of the cars, approximately 1.5m above the ground. What is the maximum communication distance between the dispatcher and a taxi?

a. 21 km

b. 30 km

c. 25 km

d. 33 km

Solution:

211. The E layer of the ionosphere aid _________ propagation and reflects _________ waves

a. MF, HF

b. HF, MF

c. LF, MF

d. MF, LF

Solution:

212. When microwave signals follows the curvature of the earth, it is known as

b. ducting

c. tropospheric scatter

d. ionospheric scatter

Solution:

213. If the polarization vector rotates 360 degrees as the wave moves one wavelength through space and field strength is equal at all angles of polarization, the polarization is _________.

a. Vertically polarized

b. Horizontally polarized

c. Circularly polarized

d. Elliptically polarized

Solution:

214. _________ travels essentially in a straight line between the transmit and the receive antennas

a. Direct waves

b. Sky waves

c. Space waves

d. Surface waves

Solution:

215. Variations brought about the revolution of the earth around the sun

a. weather variation

b. cyclical variation

c. diurnal variation

d. seasonal variation

Solution:

216. The dielectric strength of air is about 3 MV/m. Arching is likely to take place at field strengths greater than that. What is the maximum power density of an electromagnetic wave in air?

a. 40 GW/m^2

b. 15.5 GW/m^2

c. 23.9 GW/m^2

d. 18.9 GW/m^2

Solution:

217. It is a single location from which rays propagate equally in all directions

a. point source

b. omnidirectional source

c. ideal polarization

d. isotropic polarized

Solution:

218. Diffraction of electromagnetic waves

a. is caused by reflections from the ground

b. arises only with spherical waveforms

c. will occur when the waves pass through a large slot

d. may occur around the edge of a sharp obstacle

Solution:

219. The critical frequency at a particular time is 11.6 MHz. What is the MUF for a transmitting station if the required angle of incidence for propagation to a desired destination is 70 degrees?

a. 34 MHz

b. 45 MHz

c. 40 MHz

d. 15.5 MHz

Solution:

220. The rate at which energy passes through a given surface area in free space is called _________.

a. capture power

b. capture area

c. captured power density

d. power density

Solution:

221. A radio wave moves from air (relative permittivity is 1) to glass (relative permittivity is 7.8). Its angle of incidence is 30 degrees. What is the angle of refraction?

a. 10.3 degrees

b. 11.2 degrees

c. 20.4 degrees

d. 0.179 degrees

Solution:

222. It is the intensity of the electric and the magnetic fields of the electromagnetic wave propagating in free space

a. field intensity

b. field density

c. power intensity

d. power density

Solution:

223. Radio propagation was predicted mathematically by

a. Heinrich R. Hertz

b. Guglielmo Marconi

c. James Clerk Maxwell

d. Alexander Graham Bell

Solution:

224. Tropospheric scatter is used with frequencies in the following range

a. HF

b. VHF

c. UHF

d. VLF

Solution:

225. A point source that radiates power at a constant rate uniformly in all directions.

a. isotropic source

c. point source

d. any of these

Solution:

226. The transmitting distance with direct waves is limited to short distances and strictly a function of the _________ of the transmitting and receiving antenna.

a. frequency

b. phase

c. power

d. height

Solution:

227. One nautical mile is equal to _________ statute miles.

a. 2.12

b. 1.15

c. 2.54

d. 1.90

Solution:

228. It is the deflection or bending of electromagnetic waves such as radio waves, light or even sound when the waves cross the boundary line between two mediums with different characteristics.

a. reflection

b. diffraction

c. refraction

d. dispersion

Solution:

229. The reduction of power density with distance is equivalent to a power loss.

a. absorption

b. attenuation

c. distance loss

d. power dissipation

Solution:

230. The signal refracted back from the ionosphere strikes the earth and is reflected back up to the ionosphere again to be bent and sent back to earth.

a. skip transmission

b. multi-hop transmission

c. multi transmission

d. hop transmission

Solution:

231. Electromagnetic waves are refracted when they

a. pass into a medium of different dielectric constant

b. are polarized at right angles to the direction of propagation

c. encounter a perfectly conducting surface

d. pass through a small slot in a conducting plane

Solution:

232. The reduction in power density due to non free-space propagation

a. absorption

b. attenuation

c. power dissipation

d. distance loss

Solution:

233. _________ is the signal that is radiated by the antenna into the atmosphere where it is bent or reflected back to earth.

a. ground wave signal

b. sky wave signal

c. space wave signal

d. direct waves signal

Solution:

234. It is a type of fading having different effect different frequencies

Solution:

235. It is defined as the modulation or redistribution of energy within a wave front as it passes near the edge of an opaque object.

a. refraction

b. scattering

c. reflection

d. diffraction

Solution:

236. What type of modulation is primarily used in ground wave propagation?

a. Frequency modulation

b. Amplitude modulation

c. Phase modulation

d. Pulse modulation

Solution:

237. It states that every point on a given spherical wavefront can be considered as a secondary point source of electromagnetic waves from which other secondary waves or wavelets are radiated outward.

a. Hertzian principle

b. Maxwell’s principle

c. Huygen’s principle

d. Marconi’s principle

Solution:

238. Calculate the electric field intensity, in volts per meter, 20 km from a 1-kW source.

a. 3.44 mW/m

b. 7.65 mW/m

c. 8.66 mW/m

d. 1.45 mW/m

Solution:

239. The absorption of radio waves by the atmosphere depends on

a. their frequency

b. their distance from the transmitter

c. the polarization of waves

d. is always vertical in an isotropic medium

Solution:

240. Calculate the radio horizon for a 500-ft transmitting antenna and receiving antenna of 20 ft.

a. 23.1 mi

b. 31.2 mi

c. 14.8 mi

d. 37.9 mi

Solution:

241. Calculate the power received from a 20-W transmitter, 22,000 miles from earth, if the receiving antenna has an effective area of 1600 m^2

a. 4.06 x 10^-12 W

b. 2.03 x 10^-12 W

c. 1.02 x 10^-12 W

d. 0.91 x 10^-12 W

Solution:

242. As electromagnetic waves travel in free space, only one of the following can happen to them

a. absorption

b. attenuation

c. refraction

d. reflection

Solution:

243. Electromagnetic waves travelling within Earth’s atmosphere is called

a. Space wave

b. Surface wave

c. Terrestrial wave

d. Sky-wave

Solution:

244. Calculate the power density in watts per square meter (on earth) from a 10-W satellite source that is 22,000 miles from earth.

a. 3.17 x 10^-16 W/m^2

b. 6.35 x 10^-16 W/m^2

c. 2.31 x 10^-16 W/m^2

d. 1.21 x 10^-16 W/m^2

Solution:

245. It is termed used to describe variations in signal strength that occur at the receiver during this time a signal is being received.

a. skipping

b. attenuation

c. absorption

Solution:

246. The constant temperature stratosphere is called _________.

a. E-layer

b. S-layer

c. isothermal region

d. ionosthermal region

Solution:

247. It is the tendency of the sun to have grayish-black blemishes, seemingly at random times and at random place, on its fiery surface.

a. solar intensity

b. sunspot

c. solar flare

d. solar flux

Solution:

248. In electromagnetic waves, polarization

a. is caused by reflection

b. is due to the transverse nature of the waves

c. results from the longitudinal nature of waves

d. is always vertical in an isotropic medium

Solution:

249. It is an earth-guided electromagnetic wave that travels over the surface of the Earth

a. Surface waves

b. Sky waves

c. Direct waves

d. Space waves

Solution:

250. Frequencies in the UHF range normally propagate by means of

a. Ground waves

b. Sky waves

c. Surface waves

d. Space waves

Solution:

Following is the list of multiple choice questions in this brand new series:

MCQ in Radiation and Wave Propagation
PART 1: MCQ from Number 1 – 50                        Answer key: PART 1
PART 2: MCQ from Number 51 – 100                   Answer key: PART 2
PART 3: MCQ from Number 101 – 150                 Answer key: PART 3
PART 4: MCQ from Number 151 – 200                 Answer key: PART 4
PART 5: MCQ from Number 201 – 250                 Answer key: PART 5
PART 6: MCQ from Number 251 – 300                 Answer key: PART 6
PART 7: MCQ from Number 301 – 350                 Answer key: PART 7
PART 8: MCQ from Number 351 – 400                 Answer key: PART 8

### Complete List of MCQ in Communications Engineering per topic

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