Waves Flashcards
What are waves?
Something which transfers energy from one place to another, without a permanent motion of the material it is traveling through
Transverse waves
Vibrations are perpendicular to direction of energy transfer
Longitudinal waves
Vibrations are parallel to direction of energy transfer
Properties of waves
Amplitude - maximum displacement of point of wave from rest
Wavelength - distance from one point on one wave to the equal point on the wave beside it
Frequency (Hz) - number of passing a point each second
Measuring speed of sound waves practical
Method 1
1) measure point A to B with a meter stick
2) time a wave front from A to B with a stopwatch
3) speed = distance / time
Method 2
1) measure point A to B with a meter stick
2) count the number of waves between A and B
3) wavelength = distance / number of waves
4) count how long it takes for 10 waves to pass
5) frequency = 10 / time
6) speed = frequency x wavelength
Sound waves
Longitudinal waves produced by vibrations
Sound wave process
1) pinna directs sound waves into ear
2) sound waves set eardrum into oscillations, causing the small bones in the ear to oscillate
3) cochlea converts oscillations into electrical signals, sent to our brain via the auditory nerve which has hair cells along the membrane, connecting to neurones
4) within the cochlea, the base vibrates best at high frequency and the apex at low frequency
Human hearing range
20Hz to 20kHz
Speed of sound in air
330m/s
Uses of sound waves
Infrasound (<20Hz)
-seismic waves
-animal hearing
Ultrasound (>20kHz)
-medical imaging
-sonar
-medical treatment
Seismic waves
P waves (longitudinal) - travel through solid and liquid
S waves (transverse) - travel through solid only
Waves traveling from one medium to another (eg. Deep water to shallow water)
In deep water the waves travel fast and have a large wavelength. In shallow water waves travel slower, refracting towards the normal, the wavelength decreases but frequency stays the same
