Chap 2 Level 1 And 2 Flashcards
Define a wave in physics
A wave is a mechanism that transfers energy from one location to another
What are the 2 types of wave s
Electromagnetic and mechanical waves
Types of electromagnetic waves
Light
Heat
X-rays
Gamma rays
Tv signals
What is an electromagnetic wave
A transfer of energy through a varying electrical & magnetic field
What are mechanical waves
Require a physical interaction
Mechanical waves require a medium
Examples of mechanical waves
Ocean waves
Sound waves
Guitar strings
What are the two types of mechanical waves
Transverse and longitudinal
What is a transverse wave
Particles move across or perpendicular to the wave propagation direction
What are longitudinal waves
Particle motion moves across the direction of propagation
Dots represent particles
Particle closeness represents density
How does sound travel in longitudinal waves
Sound travels through compresssions and rare fractions
What are the 4 acoustic variables
Pressure
Density
Temperature
Particle motion
What is pressure
A concentration of force/area
During compressipn, pressure increases
During rare fraction, pressure decreases
Units of pressure
ATM
Mmhg
Pascals
Kg/m^2
What is density
Density = mass/volume = kg/m^3
What is temperature
Some wave energy is lost to heat in the medium due to vibrations
Temp fluctuates cyclically as concentrations move from high to low density
Parameters of wave
Freq/period = determined by wave source
Wavelength = determined by wave source and prop of medium
Propagation velocity = determined by prop of medium
Amplitude = determined by wave source
What is frequency and period
Period = how often an event occurs per time
Frequency = the # of compressions or rare fractions / time
How to Determine frequency
Determined by source
If source creates many compressions per second, high freq. few compressions, low freq
What is the period
The time that transpires between one compression to the next
What is wavelength
The physical distance between
Compressions w/in a medium
Wavelength = propagation velocity/ frequency
How to calculate amplitude
Max - mean / 2
What is constructive interference
Occurs when 2 waves interact & produce one larger wave
Waves must be identical in frequency, wavelength, and amplitude
What is destructive interference
When 2 waves are aligned that they’re max peak and min peak are the same
Completely cancels out amplitude
Classification of sound and ranges
Infrasound: 0Hz - 20hz (below human audible)
Audible: 20hz-20khz (human audible)
Ultrasound: >20khz
Diagnostic: 2Mhz-20Mhz
What is elasticity
The ability of a solid object to return its original shape after distortion by a force
What is compressability
A measure of how much the volume of the material changes for a given force
What is stiffness
Implies the inverse of elasticity of compressibility. A stiff material cannot be compressed
What is bulk modulus
High bulk
Modulus: incompressible, inelastic, stiff
Low bulk modulus: compressible, elastic, not stiff
Bulk modulus equation
C = bmodulus/density = stiffness/density
Equation for intensity
Intensity = power/area
Power is proportional to (amplitude)^2
What is the amplitude equation
20 x log(Af/Ai)
