Chapter 5 Flashcards
Electromagnetic waves
do not require a medium to travel through
includes light
Mechanical wabes
require a medium to travel through
includes sound
transverse wave
medium is displaced perpendicularly to the direction of wave propagation
Longitudinal wave
sound, medium is displaced parallel to the direction of wave propagation
velocity of wave
distance the wave travels per unit of time
v= F (wavelength)
wavelength
lambda, distance from any point in the wave to the point where the wave begins to repeat itself
frequency
number of wavelengths that pass a fixed point in one second
Period
T, time it takes the wave to travel the distance of one wavelength
T=1/f
What affects the velocity of a wave?
The characteristics of a medium (inertia and elasticity)
Decrease inertia, increase in elasticity will increase velocity
(Increase in IMF, decrease in mass)
Elasticity of medium
ability of medium to move back to original shape
more elastic means faster velocity as waves are pushed along
Inertia of medium
mediums resistance to motion, more resistance means the wave is slowed down
How does velocity of waves change is solid, liquid, and gas
V solid> V liquid> V gas
Why do sound waves travel faster in water than in air
water is denser, but has more bulk (more elasticity)
amplitude
distance between the X axis and the top of crest or bottom of trough
Always positive
Changes as the wave changes mediums
Constructive interference
sum of displacements combine to create a greater displacement
destructive interference
sum of displacements results in a smaller displacement
Phase
determines what type of interference will occur
in phase
two waves with same wavelength and begin at the same point and time
out of phase
two waves that have the same wavelength but travel different distances to arrive at the same point
Sound
transfer of energy through oscillations between high and low pressure
When is sound audible
oscillations in certain frequency trigger electrical impulses to the brain
pitch
how high or low a note sounds, corresponds to frequency
Power of a wave
rate at which a wave transfers energy
P= delta E over time
measured in intensity
intensity
average rate of energy transfer per unit area
What affects wave intensity
density of the medium, wave frequency, wave velocity
Frequency and amplitude have largest affect (squared)
Intensity level
level of loudness
ß= 10 log (I/I0)
in decibals
I0 is the intensity threshold for human hearing
if intensity factor increases by 10, the decibals increase by 10
Human threshold of hearing
10^-12vW/M^2
20-20,000 HZ
Ultrasonic waves
frequency above human hearing
US uses high frequency sound waves
waves reflect off boundaries and cause vibrations and current which is processed
intensity of waves shows density
resonance
natural and driving frequency are equal
attenuation
dampening, decrease in intensity of wave moving through a medium
Bone is denser- waves are reflected in US
Doppler effect
change in perceived frequency when a wave source and observer move towards or away from eachother
observed> source when moving toward
What happens to sound when moving towards source
distance travelled by wave is lesser
observer perceives a higher frequency
What causes beats
two waves with slightly different frequencies are superimposed
alternate constructive and destructive
Beat equation
F beat= |F0 - Fs|
Shock wave
conical wave produced when the velocity of the sound source exceeds the velocity of the sound wave
use mach number
Mach number
Vs/v
increases as the velocity of sound source increases
sonic boom
created by shock wave, as the wave fronts overlap a region of low air pressure forms
