# MCQs in Radiation and Wave Propagation Part VIII

Compiled MCQs in Radiation and Wave Propagation Part 8 of the series as one topic in Electronic System and Technologies (Communications Engineering) in the ECE Board Exam.

This is the Multiples Choice Questions Part 8 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.

### Online Questions and Answers Topic Outline

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

### MCQs in Radiation and Wave Propagation Series

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

PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V
PART 6: MCQs from Number 251 – 300                 Answer key: PART VI
PART 7: MCQs from Number 301 – 350                 Answer key: PART VII
PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII

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

351. What do you call of the travel of electromagnetic waves through a medium at the speed of light?

• a. RF propagation
• c. Wave propagation
• d. All of these

352. Electromagnetic waves are

• a. Consist of electric and magnetic component that are parallel to each other
• b. Oscillations that propagate through free space
• c. Irregular oscillations
• d. Oscillations that are produced by an oscillating circuit

353. The region around an electrically charged body in which other charged bodies are acted by an attracting or repelling force.

• a. Electric field
• c. Magnetic field
• d. Electromagnetic field

354. What are the two components of electromagnetic field?

• a. Ray and wavefront
• b. Magnet and electricity
• c. Polar electrons and magnetic field
• d. Electric field (E-field) and magnetic field

355. Shows a surface of constant phase of a wave and is formed when points of equal phase on rays propagated from the source are joined together.

• a. Ray
• b. Wavefront
• c. Point source
• d. Isotropic source

356. It is a line drawn along the direction of propagation of an electromagnetic wave used to show the relative direction of electromagnetic wave propagation.

• a. Ray
• b. Wavefront
• c. Point source
• d. Isotropic source

357. Refers to the rate at which energy passes through a given surface area in free space

• a. Field intensity
• b. Power density
• c. Refractive index
• d. Absorption coefficient

358. It it’s the intensity of the electric and magnetic fields of an electromagnetic wave propagating in free space

• a. Field intensity
• b. Power density
• c. Refractive index
• d. Absorption coefficient

359. In a lossless transmission medium, _______ of free space is equal to the square root of the ratio of its magnetic permeability to its electric permittivity

• a. Resistance
• b. Field intensity
• c. Characteristic impedance
• d. A or C is correct

360. Electromagnetic wave measures all except

• a. Inductance
• b. Power density
• c. Magnetic field intensity
• d. Permittivity of the medium

361. A reduction in power density due to the inverse square law presumes free-space propagation is called

• a. Absorption
• b. Wave attenuation
• c. Space attenuation of the wave
• d. B or C is correct

362. Which of the following are optical effects of radio waves?

• a. Refraction and reflection
• b. Diffraction and interference
• c. Induction and diffraction
• d. A and B

363. What is diffraction?

• a. Is the change in direction of a ray as it passes obliquely from one medium to another with different velocities or propagation
• b. Refers to the modulation or redistribution of energy within a wavefront when it passes near the edge of an opaque object
• c. Is the phenomenon that allows light or radio waves to travel (peek) around corners of an obstacle.
• d. A or C is right

364. A rare refracting medium has

• a. Smaller value of dielectric constant
• b. Higher value of dielectric constant
• c. Variable value for dielectric constant
• d. A dielectric constant dependent on the medium

365. Refractive index refers to

• a. The ratio of velocity of light in free space to the velocity of light in a given material
• b. The ratio of the light in free space towards the light in a given medium
• c. The ratio of the angle of refraction
• d. The amount of bending or refraction that occurs at the interface of two material of different densities

366. Why is it that rays traveling near the top of the medium travel faster than those at the bottom?

• a. The medium is more dense near the bottom
• b. The medium is less dense at the top
• c. The medium is less dense near the bottom and more dense at the top
• d. A and B are incorporated

367. When does reflection if wave occur?

• a. When an incident wave strikes a boundary of two media, and some of the incident power does not enter the second material
• b. When the reflective surface is irregular or rough
• c. When two or more electromagnetic waves combine in such a way that the system performance is degraded.
• d. A and B

368. What is meant by specular reflection?

• a. Is a reflection from a perfectly smooth surface
• b. Is an incident wavefront striking an irregular surface, randomly scattered in many directions
• c. Reflection of surfaces that fall between smooth and irregular
• d. Is a combination of diffused and semirough surfaces

369. ________ states that a semirough surface will reflect as if it were a smooth surface whenever the cosine of he angle of incidence is greater than 1/8d, where d is the depth of the surface irregularity and I is the wavelength of the incident wave.

• a. Rayleigh criterion
• b. Huygen’s principle
• c. Linear superposition
• d. Reflection coefficient

370. Energy that has neither been radiated into space nor completely transmitted

• a. Modulated waves
• b. Captured waves
• c. Standing waves
• d. Incident waves

371. What property of radio waves occurs whenever two or more waves simultaneously occupy the same point in space?

• a. Reflection
• b. Refraction
• c. Diffraction
• d. Interference

372. Pertains to a source which radiates equally in all directions

• a. Isobaric source
• b. Isotropic source
• c. Isentropic source
• d. Isothermal source

373. Electromagnetic waves travel at _____ in free space

• a. 300,000 km/sec
• b. 200 km/sec
• c. 400,000 km/sec
• d. 100,000 km/sec

374. Any space or region wherein a magnetic force is exerted on moving electric charges

• a. Electric field
• c. Magnetic field
• d. Electromagnetic field

375. Which of the following is a characteristic of electromagnetic wave?

• a. Measures power, voltage, capacitance and impedance of a system
• b. Measures power density, voltage, and inductance
• c. Measures power density, magnetic field intensity, and electric field intensity
• d. All of the above

376. Reflection waves

• a. Should take place at one medium
• b. Does not necessarily take place at one medium
• c. Occurs at any other medium at the same time
• d. Is not possible

377. Way(s) of propagating electromagnetic waves:

• a. Ground-wave propagation
• b. Space wave propagation
• c. Sky-wave propagation
• d. All of these

378. At frequencies below 1.5 MHz, what propagation provides the best coverage?

• a. Ground wave
• b. Space wave
• c. Sky wave
• d. All of these

379. Which of these causes the wavefront to tilt progressively forward?

• b. Electric field intensity
• c. Absorption coefficient
• d. Magnetic field intensity

380. Which of following of must be taken into consideration to ensure proper ground-wave propagation?

• a. Power
• b. Terrain
• c. Frequency
• d. B and C

381. What are the applications of ground–wave propagation?

• a. Ship-to-ship and ship-to-shore communications
• b. Maritime mobile communications
• d. All of these

382. The curvature of the earth presents a horizon to space wave propagation which is approximately 4/3 that of the optical horizon

• a. Standard atmosphere
• b. Optical horizon
• d. All of these

383. Refraction is caused by what factors?

• a. Changes in troposphere’s density and temperature
• b. Water vapor content
• c. Relative conductivity
• d. All of the above

384. Any of the flowing can be caused to lengthen radio horizon:

• a. Elevating the transmit or receive antennas above Earth’s surface
• b. Elevating both antennas
• c. Installing the transmit and/or receive antennas on top of mountains or high buildings
• d. All of these

385. A special condition which occurs when the density of the lower atmosphere is such that electromagnetic waves are trapped between it and earth’s surface

• a. Duct propagation
• b. Sky wave propagation
• c. Space wave propagation
• d. Ground wave propagation

386. The vibrating electrons at the ionosphere decrease current which is equivalent to reducing the dielectric constant, which in turn, will also cause the velocity of propagation to______.

• a. Increase
• b. Decrease
• c. Remain constant
• d. Decrease by a factor of 2

387. Increasing the velocity of propagation causes a/an _____ of the electromagnetic waves.

• a. Increasing refraction
• b. Decreasing reflection
• c. Increasing diffraction
• d. Decreasing interference

388. What layer has its maximum density at approximately 70 mi a noon, when the sun is at its highest point?

• a. D layer
• b. E layer
• c. Kennelly-Heaviside layer
• d. B or C

389. The sporadic E layer is a thin layer with a very high ionization density. It is considered separately from the other layers and when it appears, gives an unexpected improvement in long distance radio transmissions. What cause(s) its unpredictable appearance?

• a. Sunspot activity
• b. Sunspot cycle
• c. Solar flares
• d. A and C

390. The region in the ionosphere with a very high ionization density at roughly 55 to 90 miles and is used for frequencies up to about 20 MHz. It is gone completely at midnight.

• a. D layer
• b. E layer
• c. F layer
• d. G layer

391. A layer in the ionosphere which is the most important reflecting medium fir HF radio waves. It has 2 sublayers, at 90 to 250 mi height

• a. A layer
• b. D layer
• c. E layer
• d. F layer

392. The apparent height of the ionized layer and is always greater than the actual height

• a. Critical height
• b. Virtual height
• c. Maximum height
• d. Imaginary height

393. Refers to the shortest distance in which a sky-wave signal will be returned to the earth. It includes the maximum ground-wave range and the width of the skip zone.

• a. Hop
• b. Skip distance
• c. Actual distance
• d. Critical distance

394. Concerns to the highest frequency that is able to return to earth when beamed at a certain angle of incidence

• a. Relative frequency
• b. Optimum frequency
• c. Resonant frequency
• d. Maximum usable frequency, MUF

395. In ________, the distant of each succeeding hop from earth to ionosphere and back is also the skip distance.

• a. Hop transmission
• b. Single transmission
• c. Unihop transmission
• d. Multihop transmission

396. Concerns to the single reflection of a radio wave form the ionosphere back to earth.

• a. Jog
• b. Hop
• c. Skip

397. The fluctuation of signal strength at the receiver that are caused by changes in the transmission medium

• b. Hopping
• c. Skipping
• d. Diversity

398. Gradual variation in the field strength of a radio signal is compensated by

• b. Diversity techniques
• c. Transverse techniques
• d. Transmission techniques

399. A modulation of two different RF carrier frequencies with the same IF intelligence, then transmitting both RF signals to a given destination.

• a. Diversity
• b. Space diversity
• c. Frequency diversity
• d. Polarization diversity

400. To increase the availability of the system, a method in which the output of a transmitter is fed to two or more antennas that are physically separated by an appreciable number of wavelengths.

• a. Space diversity
• b. Frequency diversity
• c. Polarization diversity
• d. Space wave propagation

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

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