Waves Flashcards
1
Q
What is a surface wave?
A
Which particles of the medium undergo a circular motion. Surface waves are neither longitudinal nor transverse
2
Q
What is the motion of surface waves?
A
It is only the particles at the surface of the medium that undergo the circular motion. The motion of particles tends to decrease as one proceeds further from the surface.
3
Q
What is a wave?
A
A moving disturbance in the energy level of a field.
4
Q
What is medium?
A
The material or empty space through which signals, waves or forces pass.
5
Q
What is direction of propagation?
A
The axis along which the wave travels.
6
Q
Wave motion transfers _________ from one point to another, usually without permanent displacement of the particles of the medium-that is, with little or no associated mass transport
A
Energy
7
Q
Describe the motion of waves in general.
A
In physics a wave can be thought of as a disturbance or oscillation that travels through space-time, accompanied by a transfer of energy.
8
Q
What are the two types of basic waves?
A
transverse & longitudinal waves
9
Q
What is a transverse wave?
A
Composed of up-and-down movement-each end of the medium move up-and-down while the wave moves horizontally
10
Q
Transverse wave: Particles of the medium move in a direction_________to the direction that the wave moves
A
perpendicular
11
Q
What is longitudinal waves?
A
Composed of back-and-forth movement along the direction of the wave-each end of the medium moves horizontal as well as the wave
12
Q
What type of motion is present in a longitudinal waves?
A
no up-and-down motion
13
Q
Longitudinal waves: Particles of the medium move in a direction__________to the direction that the wave moves
A
parallel
14
Q
What is frequency?
A
Waves per second; measured in cycles per second
15
Q
What is Wave length?
A
Distance from one wave top (crest) to the next
16
Q
What is period or phase shift?
A
How far the wave “slides”
17
Q
What is amplitude?
A
Height of the wave
18
Q
What is speed?
A
Measured in meters per second
19
Q
What is wave part?
A
Crest is the wave top, trough is the wave bottom
20
Q
What is frequency measured in?
A
Hertz (Hz)
21
Q
What is pressure waves?
A
Can be reflected, refracted, diffracted, or absorbed (interfered) by other waves
22
Q
What is reflection?
A
Waves reflect off of a medium at the same but opposite angle; the angle of incidence is the angle at which a wave strikes a medium
23
Q
What is Refraction?
A
Redirection due to contact with a new medium
24
Q
What is Diffraction?
A
Spreading or scattering; bending around an object
25
What is interference or absorption?
Waves may interfere with other waves or be absorbed by matter.
26
What are additive when waves interfere?
Amplitudes
27
What is constructive interference?
When the crest of one wave passes through the crest of another wave or the trough of one wave passes through the trough of another wave, and the resultant wave is greater.
28
Constructive interference: Addition of two positive amplitudes or two negative amplitudes results in a _________ or _________
greater value or wave height
29
What is destructive interference?
when the crest of one wave passes through the trough of another wave.
30
Destructive interference: Amplitudes from one crest are added to the negative amplitudes from the other wave's trough, and the ___________
height of the resultant wave is decreased
31
What is another name for sound waves?
Pressure waves
32
What is sound waves?
pressure fluctuations that deviate from ambient pressure
33
How are sound waves measured?
Pascals
34
What is sound pressures?
measured on a sound pressure level that uses a logarithmic decibel scale to narrow the wide range (20 Hz to 20 kHz) of amplitudes audible to the human ear.
35
What is the wide range of decibel scale that are audible to the human ear?
(20 Hz to 20 kHz
36
What type of waves are sound waves?
longitudinal waves that propagate through matter (solid, liquid, gas) at varying speeds
37
What determines the speed of sound waves?
medium's elastic modulus (stiffness), density, and temperature
38
The speed of sound through air at 0°C is ______________.
740 miles per hour
39
What happens to sound waves when there is no matter?
In the absence of matter, there are no sound waves.
40
Sound waves do not exist in a vacuum, and only travel through _________.
matter
41
What is ultrasonography?
Sound waves above the auditory limit of the human ear (20 kHz)
42
What does ultrasonography penetrate?
These waves have power to penetrate different tissues of the body at different speed and reflect back from the tissue interface
43
What types of waves are used during ultrasonography?
Ultrasound waves to construct a visual image of internal structures by examining the reflection of sound
44
What are useful procedures that ultrasonography can assist with (3)?
intravenous catheter insertion, blocks, or transesophageal echocardiography (TEE)
45
Describe the function of ultrasonography.
a signal generator that transmits sound waves through tissues and a transducer to record the time delay for the returning reflected sound waves
46
What is the relationship between speed of sound waves and tissues?
Unique and constant to specific tissue compositions, and therefore the time delay of the returning reflected sound waves allows calculation of the location of different internal structures.
47
Ultrasonography: Will all sound waves reflect back to the transducers?
No. Some sound waves will have been refracted in a new direction, diffracted in multiple directions, or interfered with by tissues that cause attenuation or conversion to heat and resultant dissipation.
48
Ultrasonography: The fraction of the original signal that is reflected back to the transducer must be _______ and _______ into a visual display.
amplified and processed
49
What is the primary principle of ultrasonography?
Piezoelectric Effect, piezoelectric crystals that act as both signal generators and signal transducers
50
How does ultrasonography work, according to the Piezoelectric Effect?
A burst of ultrasound pressure waves is produced, followed by measurement of the reflected waves, and this process is repeated many times a second, permitting real-time imaging of internal structures by computational analysis
51
What are piezoelectric crystals?
unique quartz, ceramic, or polymer compositions that contain a matrix of polarized molecules
52
What are the two responses to piezoelectric crystals?
(1) respond to electric current by changing shape
| (2) respond to mechanical stresses by generating an electric current.
53
How does piezoelectric effect work?
A piezoelectric crystal is placed between two metal plates:
When mechanical pressure is applied to the material by the metal plates, the crystal becomes out of balance due to the electric charges generated by the applied pressure. ---Creating the waveform
54
What happens if a piezoelectric crystal is subjected to alternating electric current?
it will vibrate, creating many pressure waves in quick succession
55
Piezoelectric effect: What is the resonant frequency?
The rate at which the crystal vibrates
56
What happens to when piezoelectric crystals are not responding to an electric current?
Piezoelectric crystals are at rest and respond to the mechanical stress of the pressure waves by creating a small electric current.
57
What is common anesthesia related utilization for the piezoelectric effect?
Arterial Lines
58
How do noninvasive automated BP work?
use the piezoelectric principle to record the pressure oscillations and a microprocessor to derive the systolic and diastolic measurements.
59
How do invasive automated BP work?
Use a piezoelectric transducer that converts pressure waves into electrical signals
60
What is the Doppler effect?
the apparent change in a wave's frequency resulting from the relative velocity between the source of the waves and the observer
61
What does the doppler effect described?
Describes the change in frequency of a propagated wave from a moving object
62
Doppler Effect: The sound of a siren changes to a higher frequency as it _____ an object.
The sound of a siren changes to a higher frequency as it approaches
63
Doppler Effect: The sound of a siren changes to a lower frequency as it _________ an object
Departs
64
What is the relationship between doppler effect and echocardiography?
allows the determination of blood flow direction and speed
65
Describe the relationship between doppler effect and echocardiography.
As blood cells flow to or away from an ultrasound signal, reflected waves are either compressed or expanded. This change in frequency allows calculation of blood velocity
66
Echocardiography: If original signal shifts to a lower frequency, it means the blood is _____________.
moving away from you
67
Echocardiography: If signal shifts to a higher frequency, it means blood ___________.
Echocardiography
68
What is the color visualization if the blood is moving away from you?
Blue
69
What is the color visualization if the blood is moving towards you (Transducer)?
Red
70
What type of wave is an electromagnetic waves?
a form of transverse waves.
71
What uses electromagnetic waves?
Light, microwaves, x-rays, and TV/radio
72
What are electromagnetic waves a comb of?
electricity and magnetism, where the two wave forms are closely intertwined.
73
Anytime electricity is present, _______ will be present as well and vise versa.
Magnetism, You cannot have one form and not the other.
74
What is the motion of Electromagnetic waves?
The two waves wing in unison, but perpendicular to one another.
75
What relationship do Electromagnetic waves and matter have?
Electromagnetic waves can propagate through a vacuum; they are independent of matter.
76
What is the similarity between Pressure and Electromagnetic waves (6)?
Frequency, Amplitude, Reflection, Refraction, Diffraction and Absorption
77
What is the difference between Pressure and Electromagnetic waves (3)?
Composition, Velocity and dependence of transport medium
78
What is the composition of electromagnetic waves?
Electromagnetic waves are made of two different wave forms (electricity (velocity) and magnetism)
79
What is the Velocity of electromagnetic waves?
EMW have much higher velocity than pressure waves
80
What is the Dependence of transport medium of electromagnetic waves?
EMW can propagate through a vacuum and are independent of a transfer medium; where sound must have some form of medium to transfer its pressure wave
81
What is the speed of EMR?
300,000,000 m/sec
82
What is the speed of Sound waves?
344 m/sec
83
What is the wave type of EMR?
Transverse
84
What is the wave type of Sound waves?
Longitudinal
85
What is the energy motion of EMR?
Perpendicular to propagation
86
What is the energy motion of Sound waves?
Parallel to propagation
87
What is the inverse square law?
The intensity of a source is inversely proportional to the square of the distance form the source.
88
Waves represent the ________ of energy from a source.
propagation
89
According to the inversely square law, As energy moves away from its source, its strength _________.
decreases.
90
What are two physics properties that have the inverse square law?
Gravity and Electric force
91
The intensity of a source is _______ proportional to the square of the distance form the source.
inversely
92
What is unique about magnets?
form of matter in which the charges are aligned in an orderly fashion
93
What is present in all magnets?
flows of magnetic currents, or field lines
94
How can u view the power of magnets?
To observe these invisible fields, place a magnet under a piece of paper and spread iron filings on top. The filings will line up along the magnetic fields.
95
What is magnetism?
Is a force between electric currents
96
What is important about flowing charged particles?
not only move energy along that current, but also disrupt, or alter, the surrounding environment
97
What is the components of MRI?
Uses a strong, continuous magnetic field to uniformly realign the spin of protons within the hydrogen atoms of water
98
How does MRI work?
As the proton axes are pulled into one of two possible realigned positions, a radiofrequency pulse is delivered at resonant frequency to energize the protons. The protons will then reemit this energy. The radiofrequency pulses are delivered in thin “slices” that may be made in the sagittal, coronal, or axial planes. Computer-generated analysis of these data produces very detailed representations of internal tissues.
99
As the proton axes are pulled into one of two possible realigned positions, a _______ pulse is delivered at resonant frequency to energize the protons.
radiofrequency
100
What kind of magnets are used in MRIs?
Superconductor magnets
101
What are superconductor magnets?
These magnets are electromagnets where the coil is submerged in liquid helium at a very low temperature. At this low temperature, the coil becomes a superconductor.
102
Why is certain safety precautions needed in the MRI?
Due to the high strength of the magnetic field created
103
Any __________ material will interact with the magnetic field, gaining kinetic energy and thermal heat
ferrous
104
Why is MRI safety so important?
Patients and personnel are at potential risk for both thermal injuries from implanted ferrous objects and traumatic injury from ferrous objects violently pulled into the magnetic field
105
What is important to know about the MRI environment?
divided into four zones that correlate with the intensity of the magnetic field and the risk to patients and health care providers.
106
Who designated the four MRI safety zones?
American College of Radiology
107
Which MRI zone has the greatest risk of injury and the most stringent guidelines?
Zone 4
108
What must be removed when entering into zone 4?
All ferrous materials such as pagers, phones, jewelry, identification badges, and pens must be removed before entering zone 4. Patient stretchers, oxygen tanks, IV poles, and any other ferrous objects must be kept outside zone
109
What occupants can be allowed in Zone 1 of the MRI?
General public
110
What occupants can be allowed in Zone 2 of the MRI?
unscreened MRI patients
111
What occupants can be allowed in Zone 3 of the MRI?
Screened MRI patients and personnel
112
What occupants can be allowed in Zone 4 of the MRI?
Screen MRI patients under constant direct supervision of trained MRI personnel
113
What type of hazards are possible in zone I of the MRI?
Negligible
114
What type of hazards are possible in zone 2 of the MRI?
Immediately outside area of hazard
115
What type of hazards are possible in zone 3 of the MRI?
Potential biostimulation interference, access to magnet room
116
What type of hazards are possible in zone 4 of the MRI?
Biostimulation interference, radiofrequency heating, missle effect, cryogens
117
Wave energy causes ______ and _________ to occur along its path.
Compression and Decompression (Rarefaction)
