Waves Flashcards
purpose of waves
to transport energy
longitudinal waves
particles of medium vibrate/ oscillate in the same direction as the energy travels
transverse waves
particles of medium vibrate/ oscillate at right angles to the direction of travel of the wave
amplitude
the maximum extent of a vibration or oscillation
crest
a point on wave with the maximum value/ highest point of upward displacement within a cycle
trough
a lowest point on wave with the minimum value of downward displacement within a cycle
transverse wave wavelength
minimum distance in which a wave repeats itself
frequency
number of waves that pass a point every sec (hertz)
period
time for one complete wave
the wave equation
wave speed = frequency x wavelength
frequency=1/time period
conclusion for slinky experiment:
the longer the slinky is stretched…
the faster the wave speed of a pulse travels along the slinky
conclusion for pendulum experiment:
the long the length of the pendulum…
the greater the time period, but the rate decreases slowly
what are sound waves?
vibrating air molecules
how many hertz can the human ear typically hear?
from 20hz-20000hz
what are sounds 20000+ hz called?
ultrasonic
for longitudinal waves, what does a high pitch result in the shape of the wave?
high frequency (distance between waves closer)
for longitudinal waves, what does a loud sound result in the shape of the wave?
large amplitude (height of the wave larger)
speed of sound in air
340m/s
things that have transverse waves
radio, infra red, water, skipping rope, guitar string
things that have longitudinal waves
sound
what surface reflect sounds better and what absorb sounds better? which one makes noise sound clearer?
polished surfaces; soft object surfaces; soft object surfaces
what is ultrasound?
sound waves of frequencies greater than 20000hz, above the upper limit of the hearing range for humans
how are ultrasounds made?
made by electronic systems which produce electrical oscillations which are used to generate the ultrasonic waves
uses of ultrasonic waves
- pre-natal scanning
- echo-sounding
- cleaning delicate objects
- detecting flaws and cracks
- echo-location by bats
how does ultrasonic waves work for pre-natal scanning, echo-sounding, detecting flaws and cracks?
time delay of reflections can be used to calculate the depth of/ size of and distance to the reflecting surface
how does ultrasonic waves work for cleaning delicate objects? what benefits does this have?
the vibrations of the ultrasonic waves dislodge dirt particles from the surface of the object, ensuring that there’s no danger of breakage or need to disassemble the object
why is it important to have a very narrow beam of ultrasound waves?
it gives us a focused detailed image
what is resonance frequency?
when the driving frequency equals the natural frequency of an object, the oscillations become larger
4 layers in earth’s structure
crust, mantle, outer core, inner core
primary waves (p waves) characteristics
longitudinal and faster (6km/s), can travel through all air, liquid and rock
secondary waves (s waves) characteristics
transverse and slower (4km/s), can only travel through solids
longitudinal wave compression
a region in a longitudinal wave where the particles are closest together
longitudinal wave rarefaction
a region in a longitudinal wave where the particles are furthest away
longitudinal wave wavelength
length between two points of compression or two points of rarefaction
why do the paths of the waves bend as they travel through the earth?
because there are changes in composition, pressure and temperature within the layer of the earth so they travel at different speeds though different materials
why is there an s wave shadow zone?
because s waves can’t travel through anything not solid
what does the shadow zone tell us about the earth’s structure?
the earth has a solid mantle and a liquid core
how can tall buildings be made earthquake proof?
flexible foundations, damping, vibration deflection technology, shear walls, cross braces, diaphragms and moment-resisting frames
explain how resonance is related to the height of a building during an earthquake
taller buildings tend to experience more prolonged and sustained shaking than shorter ones because they often have lower damping naturally, meaning that they don’t restrain or reduce energy of vibratory motion and amplitude of oscillations that much
