Waves Flashcards
Longitudinal waves direction of particles
Back & forth to the direction of the wave
Transverse waves direction of particles
Move up & down perpendicularly to the direction to the wave
One way of measuring speed of waves in the sea
Measure the time it takes for one wave to pass between two fixed points such as bouys
One way of measuring speed of sound with a wall is
Measure how long it takes for the echo to reach back to you
Core practical for speed of water waves
Ripple tank
Straight dipper - generates waves due to movement in water
Ruler to estimate wavelength
Count waves in 10 secs for frequency
When water goes from deep to shallow what happens
It changes direction and slows down
Ear
Pinna captures waves and ushers them down ear canal
Hits membrane called ear drum which vibrates
Vibrations hit anvil, hammer and stirrups which vibrate and amplify the vibrations
Travels to cochlea where fluid inside vibrates. Cillia in cochlea detect vibrations and change them to electric impulses that travel down the auditory nerve to the brain
Base of cochlea is and does
Thicker and detects 20,000HZ
Apex of cochlea is and detects
Thin and detects 200HZ
Why does cochlea membrane change in thickness
Different frequencies vibrate best at different thicknesses.
How do ships use ultrasound waves
Sonar
Emits pulses down and counts the time it takes to detect them
Speed x time/2 = depth
How do ultrasound scans work
A gel is used to stop the ultrasound waves from reflecting if the skin
The probe emits and receives and count the time between the pulses. The screen shows where the ducks are coming from - further down the screen is the longer it is.
Infrasound
Less than 200 Hz
P waves
Longitudinal
Travel through solids liquids and gases hence small shadow zone.
Some weak p waves in shadow zone meant that they had to be reflected off a solid inside the liquids core proving we have a solid inner core
S wave
Transverse
Only through solids
Large shadow zone because it can’t pass through liquids inner core
