part 2 Flashcards
it is the reduction in power density with distance is equivalent to a power loss
wave attenuation
free space is a vacuum, so (no loss, there is loss) of energy as a wave propagates through it.
no loss
because the attenuation is due to the spherical spreading of the wave, it is sometimes called _________.
space attenuation
it is generally expressed in terms of common logarithm of the power density ratio.
wave attenuation
as an electromagnetic wave passes through the atmosphere, it interchanges energy with free electrons and ions. this type of reduction of power is called _______.
absorption loss
which statement is correct
a. the lesser the particle density, the greater the possibility of collissions and the greater the absorption.
b. the lesser the particle density, the lesser the possibilty of collisions and the greater the absorption.
c. the greater the particle density, the greater the possibility of collisions and the greater the absorption.
d. the greater the particle density, the greater the possibility of collisions and the lesser the absorption.
c. the greater the particle density, the greater the possibility of collisions and the greater the absorption.
it is the reduction in power density due to non free-space propagation
absorption
it is the reduction in power density due to inverse square law presumes free-space propagation
wave attenuation
______ causes severe absorption at microwave frequencies.
precipitation
reflection : bouncing :: diffraction : _______
scattering
refraction : bending :: interference : ____________
colliding
it is sometimes referred to as the bending of the radio-wave path. however, ray does not actually bend.
refraction
it is actually the changing of direction of an electromagnetic ray as it passes obliquely from one medium into another with different velocities of propagation.
electromagnetic refraction
in refraction, the velocity of propagation at which an electromagnetic wave propagates is (inversely, directly) proportional to the density of the medium in which it is propagating.
inversely
Refraction of electromagnetic waves can be expressed in
terms of refractive index of the atmosphere it is passing
through. Mathematically, it is _________. (the formula)
the square root of the
dielectric constant.
𝒏 = sqrt Er
The amount of bending or refraction that occurs at the
interface of the two materials of different densities _____________.
a. depends on the refractive index of the two materials.
b. depends on the reflective index of two materials.
c. depends on the refractive index of one material.
d. depends on the reflective index of one material.
a. depends on the refractive index of the two materials.
it is simply the ratio of the velocity of a light ray in FREE SPACE to the velocity of propagation of a light ray in a GIVEN MATERIAL.
refractive index
refractive index can be mathematically expressed as ________
n = c/Vp
the relationship between the angles and the indices of refraction is given by a formula known as _____________.
snell’s law
what is the formula for snell’s law
n1sinθi = n2sinθr
in the formula of snell’s law, n1 is the ___ while n2 is the __.
n1 = index of refraction of the initial medium
n2 = index of refraction of medium into which wave proagates
In extreme cases, where the angle of incidence is large
the wave travels into a region of considerably lower
dielectric constant, the angle of refraction can be greater
that 90˚, so that the wave comes out of the second
medium and back into first. refraction becomes a form of reflection and this is called ________.
total internal reflection
it is the angle of incidence that results in an angle of refraction of exactly 90˚
critical angle
what is the given formula for critical angle
θc = (sin^-1)(n2/n1)
it occurs when an incident wave strikes a boundary of two media and some or all of the incident power does not enter the second material.
electromagnetic reflection
Saying all the reflected waves remain in medium 1, the
velocity of the reflected and incident waves are _______.
equal
The angle of reflection equals to the angle of incidence. the reflected voltage intensities is ______ than the incident voltage field intensity.
less
it is the ratio of the reflected and incident power densities
reflection coefficient (Γ)
it is the portion of the total incident power that is not reflected
power transmission coefficient (T)
for a perfect conductor, T=____
0
it is the fraction of power that penetrates medium 2
absorption coefficient
When an incident wavefront strikes an irregular surface, it
is randomly scattered in many directions. Such condition is called ______.
diffused reflection
Whereas reflection from a perfectly smooth surface is called _________.
specular (mirrorlike) reflection
Surface that fall between smooth and irregular is called _______.
semi-rough surfaces
this states that a semi-rough surface will reflect as if it were a smooth surface whenever the cosine of angle of incidence is greater than 𝛌/8d, where d is the depth of irregularity.
rayleigh criterion
it is the bending of waves around an object. it is also defiened as the modulation or redistribution of energy within a wavefront when it passes near the edge of an opaque object.
diffraction
this phenomenon allows light of radio waves to propagate (peek) around corners.
diffraction
he is the founder of the wave theory of light
christian huygens
this states that every point on a given spherical wavefront can be considered as a secondary point source of electromagnetic waves from which the other secondary waves are radiated outward.
huygen’s principle
As the wave front passes the object, the point sources of waves at the edge of the obstacle create additional spherical waves that penetrate and fill in the shadow zone. This phenomenon, sometimes called, ______.
knife-edge diffraction
_________ result from the superposition of oscillations or waves of same nature and equal frequency.
interferences
it is the mode of propagation wherein different waves propagated along such multiple paths interfere at the reception.
multipath propagation
