P5.1 Flashcards
Vibrations
Back and forth motion, when something is displaced from its’ equilibrium position
Sound waves
A wave produced by a vibration. REQUIRES A MEDIUM IN ORDER TO TRAVEL
Do electromagnetic waves need a medium?
NO
Longitudinal waves
When the direction of vibration is parallel to the direction of energy transfer
Transverse waves
When the direction of vibration is PERPENDICULAR to the direction of energy transfer
Amplitude
Distance from the peak/trough to the principle axis/normal line
Wavelength
Distance from one peak/trough to the next
Frequency
Number of oscillations/peaks passing through a point in one second
Time period
Time for one wave to pass a given point
Which part of a wave diagram represents HIGH PRESSURE?
Peak
Which part of a wave diagram represents LOW PRESSURE?
Trough
Wave velocity
The speed at which the energy of a wave is transferred
Unit for time period
Seconds, s
Time period equation
1 / frequency
Wave equation
Wave speed (m/s) = frequency (Hz) x wavelength (m)
Wave compression
High pressure- particles squashed together
Wave rarefaction
Low pressure - particles spread far apart
How can one physically model waves?
Using ripples in water ONLY FOR TRANSVERSE WAVES
How to measure the velocity of ripple in water?
Using a ripple tank, u already know the frequency at which the machine is making them.
Calculate wavelength by using a strobe (flashing light) and a ruler
How to Measure velocity of sound waves?
OSCILLOSCOPE - device that shows a changing P.D
Uses same idea of how microphones work
2 facteors affecting velocity of a sound wave
Temperature
Pressure
Refraction
Change in wave direction when the speed changes whilst going from one medium to another
Does the frequency of a wave ever change?
NO, THE FREQUENCY OF EACH WAVE IS UNIQUE AND CONSTANT.
It helps to identify the wave, so if the frequency changes, then the wave will not be the same
3 possibilities when a wave hits a boundary
- reflects (e.g. echo)
- transmitted
- absorbed
IT DEPENDS ON THE DENSITIES OF THE REGION ON EITHER SIDE OF THE BOUNDARY
Frequency of ultrasound
Greater than 20,000 Hz - hence we can’t hear it, beyond human ear range
How does ultrasound produce images of a baby?
- ultrasound beam is sent into mother
- waves reflect off the different boundaries of the baby
- machine calculates distance, using time taken and velocity of the wave and uses the distances to produce an image.
What does the outer ear (pinna and auditory canal) do ?
Gather the sound waves and directs it to the ear drum ,which then vibrates
What does the vibration of the ear drum cause?
It causes the ossicles to vibrate. These amplify the vibration and pass it to the inner ear through the oval window
Where does the oval window lead to?
The cochlea. It is a snail shell shape and is filled w/ liquid
- transmits the movement of the oval window to the small hairs on the inside wall of the cochlea
- hairs are attached to sound detecting cells that release chemical substances when stimulated
- makes nerves send a signal down the auditory canal to the brain
- brain processes the signal and you hear the sound.
Resonance
The large amplitude oscillation that happens when u make something vibrate @ its’ natural frequency
Natural frequency
The frequency at which an object vibrates/oscillates if it is displaced
(E.g. for humans it is 20Hz to 20,000Hz - the parts of the ear cannot vibrate slower or faster than this)
