Radiation and Propagation of Waves

Question 1

What is Maxwell’s theory?

Answer 1

theoretical basis of all electromagnetic waves that propagate through space at the speed of light.

Question 2

Hertz confirmed Maxwell’s prediction when he

Answer 2

generated and detected electromagnetic waves in 1887.

Question 3

Electromagnetic waves are generated by

Answer 3

oscillating electric charges

Question 4

Electromagnetic waves carry

Answer 4

energy and momentum

Question 5

Developed the electromagnetic theory of light

Answer 5

James Clerk Maxwell

Question 6

James Clerk Maxwell also developed:

Answer 6

o Kinetic theory of gases
o Nature of Saturn’s rings
o Color vision

Question 7

First to generate and detect electromagnetic waves in a laboratory setting.

Answer 7

Heinrich Rudolf Hertz

Question 8

The most important discoveries were in

Answer 8

1887

Question 9

is an idealized wave environment where there is no other transverse electromagnetic (TEM) wave, no gravity, no obstructions, no atmosphere, no celestial events, no terrestrial events, no electrical noise, and no observers. In short, the wave environment is free from everything except the wave itself

Answer 9

Free Space

Question 10

space that does not interfere with the normal radiation and propagation of waves (epitome of nothingness).

Answer 10

free space

Question 11

time phase and space quadrature

Answer 11

that the E and H fields rise and fall together in time but are 90 degrees apart in space.

Question 12

The orientation of the E-field component of the wave

Answer 12

Polarization

Question 13

The bending of a radio wave when it passes obliquely from one medium to another in which the velocity of propagation is different.

Answer 13

Refraction

Question 14

The scattering of waves as it passes the edges of an object or opening. Diffraction is defined as the modulation or redistribution of energy within a wavefront when it passes near the edge of an opaque object

Answer 14

Diffraction

Question 15

allows light or radio waves to propagate (peek) around corners.

Answer 15

diffraction

Question 16

occurs when two or more electromagnetic waves combine in such a way that system performance is degraded

Answer 16

interference

Question 17

• Propagation of radio waves in the atmosphere is greatly influenced by the

Answer 17

Frequency of the wave

Question 18

three possible modes of propagation:

Answer 18

-Ground/surface wave propagation
-Sky wave propagation
-Space Wave Propagation

Question 19

start out with the electric field being perpendicular to the ground. Due to the gradient density of the earth’s atmosphere the wavefront tilts progressively

Answer 19

Ground waves

Question 20

Advantages of ground wave propagation

Answer 20

• Given enough power, can circumnavigate the earth.
• Relatively unaffected by atmospheric conditions.

Question 21

Disadvantages of ground wave propagation

Answer 21

• Require relatively high transmission power.
• Require large antennas since frequency is low.
• Ground losses vary considerably with terrain

Question 22

Applications of Ground Wave Propagation

Answer 22

MF broadcasting; ship-to-ship and ship-to-shore communications; radio navigation; maritime communications.

Question 23

HF radio waves are returned from the F-layer of the ionosphere by a form of refraction

Answer 23

Sky wave propagation

Question 24

The highest frequency that is returned to earth in the vertical direction is called the ___________. The highest frequency that returns to earth over a given path is called ___________.

Answer 24

critical frequency, fc
maximum usable frequency (MUF)

Question 25

Application of sky wave propagation

Answer 25

Almost all HF propagation, and nighttime long distance MF propagation is by sky wave.

Question 26

Above ______, waves are more likely to penetrate the ionosphere and continue moving out into space.

Answer 26

30MHz

Question 30

• Is a special case of skywave propagation used for frequencies higher than those in standard skywave propagation technique.

Answer 30

Tropospheric Scatter

Question 30

Is used when reliable long distance communication link is needed across deserts, mountain regions, offshore drilling platform and between distant islands.

Answer 30

Tropospheric Scatter

Question 30

Travel in a straight line from the transmitting antenna to receiving antenna

Answer 30

Space-wave Propagation

Question 30

• At frequencies ______ ground wave is best.
• Sky waves are used for ___________.
• Space waves are used for ____________.

Answer 30

< 2 MHz,
HF
VHF and above