US Physics Wk 1

two terms that are not associated

unrelated

two items that are associated

*relationship does not have to be specified*

related or proportional

two items that are directly associated, such that when one item increases the other one will increase

directly relational/proportional

two items that are associated such that when one increases, the other decreases

inversely related/proportional

when two numbers of a reciprocal relationship are multiplied together, the result is

one

this is a special form of an inverse relationship

reciprocal

increase by a factor means to

multiply by that number

decrease by a factor means to

divide by that number

a number alone without a unit is called

ambiguous

- meter

- centimeter

- feet

units of length

- cm^2

- squared

units of area

- cm^3

- cubed

units of volume

a number written in scientific notation with a positive exponent has a value greater than

10

a number written in scientific notation with a negative exponent has a value less than

1

a number written in scientific notation with an exponent of zero has a value between

1-10

a traveling variation in one or more quantities

wave

2 types of waves:

longitudinal and transverse

wave where particles move in a direction that is perpendicular to the direction that the wave propagates

transverse wave

light is a _______ wave

transverse

wave where particles move in the same direction that the wave propagates

longitudinal wave

sound is a __________ wave

longitudinal

a mechanical wave in which particles in the medium vibrate back and forth from a fixed position

sound wave

when sound travels through a medium, the molecules undergo a series of (2)

compressions and rarefactions

areas of increased pressure and density

compressions

areas of decreased pressure and density

rarefactions

the effects of the medium upon the sound wave

acoustic propagation

the effects of the sound wave on biologic tissue

biologic effects

a sound wave is also called an _________ wave

acoustic

there are ____ acoustic variables used to distinguish a sound wave from other waves

3

3 acoustic variables:

pressure, density, distance

the concentration of force in an area

pressure

units for pressure

Pascals (Pa)

concentration of mass in a volume

density

units for density

kg/m³ (mass per volume)

measure of particle motion

distance

units for distance

cm, mm

occurs when the peaks and troughs of the 2 waves occur at the same time and same location

in-phase waves

maximum value of wave

peak

minimum value of wave

trough

occurs when the peaks and troughs are at different times and locations

out-of-phase waves

when multiple sound beams are traveling in the same medium and arrive at the same location and time- combining to form a single wave

interference

interference may be (2)

constructive or destructive

interference that takes place with in-phase waves

constructive

this results in a single wave of greater amplitude than either of its components

constructive interference

interference that takes place with out-of-phase waves

destructive

this results in a wave smaller than one of its components

destructive interference

when two waves of equal amplitude but opposite waveforms occur, _________ interference can occur

complete destructive interference

there are ___ parameters used to describe sound waves

7

period

frequency

amplitude

power

intensity

wavelength

propagation speed

parameters used to describe sound waves

the time it takes a wave to vibrate a single cycle

(time from the start of one cycle to start of next cycle)

period

units for period

units of time

seconds, hours, days

period is determined by ________ only

sound source

typical values of period

0.06 to 0.5 microseconds

Period ______ be changed by sonographer

cannot

the number of particular events that occur in a specific duration of time

frequency

in US, frequency of a wave = the number of _______ per second

cycles

units for frequency

Hz

typical values of frequency

2MHz to 15 MHz

frequency is determined by ______ only

sound source

sound with frequency less than 20 Hz

infrasound

sounds with frequencies between 20-20,000 Hz

audible sound

sound with frequency higher than 20,000 Hz

ultrasound

Frequency _____ be changed by the sonographer

cannot

frequency and period have an ______ relationship

inverse

as frequency increases, period

decreases

period and frequency are also reciprocals, so period x frequency =

1

______ = 1 event per second

1 Hz

the bigness parameters include

amplitude, power, intensity

the difference between the maximum or minimum value and the average value of an acoustic variable

amplitude

typical values for amplitude

1 MPa - 3MPa

amplitude _____ be changed by sonographer

can

amplitude is determined by the _______ only

sound source

the difference between the maximum and minimum values of an acoustic variable

peak-to-peak amplitude

the rate at which work is performed/energy is transferred

power

units for power

watts

typical values for power

0.004 to 0.090 watts

power is determined by ______ only

sound source

power _____ changed by sonographer

can be

amplitude and power describe the _________ of a wave

magnitude

when power increases, amplitude

increases

power is proportional to the waves amplitude _____

squared

the concentration of energy in a sound beam

intensity

intensity =

power/area

units for intensity

W/cm²

typical values for intensity

0.01 to 300 W/cm^2

intensity is determined by the ______ only

sound source

Intensity _______ be changed by the sonographer

can

if a waves power is doubled, the intensity is

doubled

if a waves amplitude is doubled, the intensity increases ______ the original value

4 times

the distance/length of one complete cycle

wavelength

units of wavelength

mm, meters, any unit of length

typical value of wavelength in soft tissue

0.1 to 0.8 mm

wavelength is determined by

both the source and medium

wavelength ______ be changed by sonographer

cannot

wavelength = _________ while period = time

distance

as frequency increases, wavelength

decreases

lower frequency = ________ wavelength

longer

wavelength of 1 MHz in soft tissue

1.54 mm

the rate at which a sound wave travels through a medium

propagation speed