Module 10—Introduction to Wave Propagation, Transmission Lines, and Antennas Flashcards
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AN OPERATING PROCEDURE, PRACTICE, OR CONDITION, ETC., WHICH MAY
RESULT IN INJURY OR DEATH IF NOT CAREFULLY OBSERVED OR
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Caution
AN OPERATING PROCEDURE, PRACTICE, OR CONDITION, ETC., WHICH MAY
RESULT IN DAMAGE TO EQUIPMENT IF NOT CAREFULLY OBSERVED OR
FOLLOWED.
Note
An operating procedure, practice, or condition, etc., which is essential to emphasize
Propagation (definition)
movement through a medium (such as light rays)
Radio waves are
radiant energy (such as light or heat)
Radio waves travel at
the speed of light
A wave can be defined as
DISTURBANCE (sound, light, radio waves) that moves through a MEDIUM (air, water, vacuum).
Wave motion can be defined as
a recurring disturbance advancing through space with or without the use of a physical medium. Wave motion, therefore, is a means of moving or transferring energy from one point to another point.
Transverse Wave Motion (definition)
The up and down motion at right angles to the
outward motion of waves (ex. in the case of a stone being dropped in water, the water is not actually being moved outward by the motion of waves, but up
and down as the waves move outward).
Wavelength (definition)
the distance from the crest of one wave to the crest of
the next, or between any two similar points on adjacent waves.
Water waves are known as
transverse waves
The amplitude of a transverse wave is
half the distance measured vertically from the crest to the trough
Types of transverse waves
water, radio, light, heat (sound is longitudinal)
radio, light and heat waves are examples of
transverse waves
Sound waves are known as
longitudinal waves
Sound waves travel
back and forth in the same direction as the wave motion. Therefore, longitudinal waves are waves in which the disturbance takes place in the direction of propagation.
Longitudinal waves are sometimes called
Compression waves
Compression waves are usually called
Longitudinal waves
They’re called compression waves because
air is elastic, and when the material (ex. tuning fork tines) moves outward, the air in front of it is compressed so that it’s momentary pressure is raised above that at other points in the surrounding air. (air in this case is the medium.)
rarefied (definition)
something made less dense. or expanded. the air pressure is lowered below that of the other points in the surrounding medium. (the air.) (the opposite of a compression wave, such as when a tuning fork tine moves inward rather than out)
a medium (definition)
the vehicle or means though which the wave travels from one point to the next
a source is
the object producing the waves
an object responding to the waves is called
a detector or a reciever
a detector (definition)
an object responding to the waves
a receiver (definition)
an object responding to the waves
the three requirements for a wave to be propagated
source, medium and detector/receiver
with the exception of electromagnetic waves, which don’t require a medium
reference line (definition)
a rest position or point of zero displacement
point of zero displacement (definition)
a rest position or reference line
positive alternation (definition)
the portion of a wave above the reference line
negative alternation (definition)
the portion of a wave beneath the reference line
the crest (definition)
the peak of the positive alternation of a wave
the trough (definition)
the peak of the negative alternation of a wave
wavelength (definition)
the distance in space occupied by one cycle of a radio wave at any given instant
λ (lambda) is the symbol for
wavelength
L is the symbol for
inductance
I is the symbol for
dimensional length
frequency (definition)
the number of cycles (vibrations) of a wave train in a unit of time
cps (definition)
cycles per second (also known as Hertz)
hertz (definition)
cycles per second
the two types of wave motion
transverse and longitudinal
velocity of propagation (definition)
the rate at which the disturbance travels through the medium, or the velocity with which the crest of the wave moves along
the higher the frequency
the greater the number of compressions and expansions per unit of time
period (definition)
the time in which one complete vibratory cycle of events occurs
f is the symbol for
frequency
t is the symbol for
time
proper units of length
if the velocity (expressed in feet per second) is divided by the frequency (expressed in cycles per second, or Hz), the wavelength is given in feet per cycle. If the metric system is used and the velocity (expressed in meters per second) is divided by the frequency (expressed in cycles per second), the wavelength is given in meters per cycle. Be sure to express both the
wavelength and the frequency in the same units.
wave velocity (definition)
the speed with which a wave train passes a fixed point
reflection wave (definition)
wave that is neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter
incident wave (definition)
a wave directed toward the surface of the mirror
reflected wave (definition)
the wave when it bounces off the mirror
the normal (definition)
the perpendicular, or the point at which the incident wave strikes the mirror’s surface
the angle of incidence (definition)
the angle between the incident wave and the normal
the angle of reflection (definition)
the angle between the reflected wave and the normal
law of reflection
the angle of incidence is equal to the angle of reflection
transfer of energy is greatest when
the wave is nearly parallel to the reflecting surface
transfer of energy is least when
the incident wave is perpendicular to the surface
refraction (definition)
when the wave changes direction due to passing into another medium that has a different velocity of propagation
the angle of refraction (definition)
the angle between the normal and the path of the wave through the second medium
if the wave passes from a less dense medium to a more dense medium
it is bent toward the
normal, and the angle of refraction (r) is less than the angle of incidence (i)
if the wave passes from a more dense to a less dense medium
it is bent away from the normal, and the angle of refraction (r1) is greater than the angle of incidence (i1)
diffraction (definition)
the bending of the wave path when the wave meets an obstruction
am band radio waves are
lower frequency
fm band radio waves are
higher frequency
doppler effect (definition) assumes the frequency at the source is constant
the apparent change in frequency or pitch when a sound source moves either toward or away from the listener, or the listener moves away from the source
