waves Flashcards
waves do what
Waves transfer energy from one place to another without transferring matter.
amplitude
the maximum displacement from the equilibrium position (the x-axis).
wavelength
the distance of one entire oscillation of that wave.
time period
the time it takes for one entire oscillation of a wave.
frequency
The total number of wave cycles completed in one second
The formula for frequency is:
frequency=1/time
(time when one complete oscillation)
The formula for wave speed is:
wave speed (metre/second, m/s) =
frequency (hertz, Hz) × wavelength (metre, m)
parallel to the direction of energy transfer is a:
Longitudinal
perpendicular to the direction of energy transfer is a
Transverse wave
examples of transverse wave
light
radio
ripples
waves on strings for guitar
examples of longitudinal waves
sound
seismic p waves
Describe one piece of evidence that shows when a sound wave travels through the air it is the wave and not the air itself that travels
A vibrating drum skin does not move the air away to create a vacuum (around the drum).
period
length of time it takes one wave to pass a given point
velocity
speed of the wave in the direction that its travelling
Describe how to measure the velocity of sound in air and
ripples on water surfaces
sound- stand infront of large wall measure the time it takes for an echo of loud sound to reach you
velocity-measure the time it takes for a wave to travel between two fixed points such as buoys
Calculate depth or distance from time and wave velocity
distance=speedx time
is there is an echo divide by 2
reflection
when a wave bounces off a boundry
refraction
when a wave passes into an new material but changes speed and direction when travelling
transmission
when a wave passes through a material and is not absorbed or reflected
absorbtion
when a wave dissapears as the energy it is carrying is transferred into a new material
Explain how waves will be refracted at a boundary in terms of
the change of direction and speed
When wave crosses boundary between materials at angle changes direction which means refracted
- Waves crosses a high density material a slower wave
wave crossing low density material will have a higher speed
3 how much wave speeds up or slows down will affect refracted.
wave crosses boundry and slows down bends towards normal
sppeds up bend away from normal
- The wavelength of wave changes when refracted, but frequency stays the same
- If the wave is travelling along the normal it will change speed, but it’s not refracted
27 / 29
Recall that different substance may absorb, transmit, refract or reflect EM waves in ways that vary with WL
different WL will A,T,R differently
just like how light waves through glass will be A,TR etc
Describe the processes which convert wave disturbances between sound waves and vibrations in solids
Sound example longitudinal wave -
compressions (regions of higher density)
rarefactions (lower density).
These cause changes in pressure,
vary in time with the wave.
waves hit the solid, the variations in pressure cause the surface of the solid to vibrate in sync with the sound wave.
Explain why such processes only work over a limited frequency range, and the revelance of this to human hearing
NOT ABOUT THE VOLUME (like tv volume)
as humans range of frequencies that we can hear. animals have different.
Hair cells become damaged which cant receive the vibrations
Recall that sound with frequencies greater than
20 000 hertz, Hz, is known as
ultra sound
Recall that sound with frequencies less than 20 hertz,
Hz, is known as
infrasound
explain uses of ulta sound
Sonar
uses ultrasound detect objects underwater
The sound wave is reflected off the ocean bottom
The time sound wave return used to calculate the depth of the water
The distance the wave travels is twice the depth of the ocean
This is the distance to the ocean floor x2
Foetal Scanning
ultrasound used images of a foetus in the wombmade up of a transducer that produces and detects a beam of ultrasound waves into the body
waves are reflected back to the transducer by different boundaries between tissues in the path of the beam
For example, the boundary between fluid and soft tissue or tissue and bone
exploration of earths core
p waves - move faster than s waves
longitudinal but cant pass gas
low frequency sound waves known as infrasound
s waves
S-waves are slower than P-wave
unable to travel through liquid
only travel through solids
explain uses of ulta sound
Sonar
uses ultrasound detect objects underwater
The sound wave is reflected off the ocean bottom
The time sound wave return used to calculate the depth of the water
The distance the wave travels is twice the depth of the ocean
This is the distance to the ocean floor x2
Foetal Scanning
ultrasound used images of a foetus in the wombmade up of a transducer that produces and detects a beam of ultrasound waves into the body
waves are reflected back to the transducer by different boundaries between tissues in the path of the beam
For example, the boundary between fluid and soft tissue or tissue and bone
exploration of earths core
p waves - move faster than s waves
longitudinal but cant pass gas
low frequency sound waves known as infrasound
s waves
S-waves are slower than P-wave
unable to travel through liquid
only travel through solids
what does the discovery of p and swaves show
The mantle is solid – this is because both types of wave can pass through it
The outer core of the Earth is liquid – hence no S-waves can penetrate it
The inner core is solid – this is due to the size and positions of these shadow zones which indicate large refraction taking place
Describe how changes, if any, in velocity, frequency and
wavelength, in the transmission of sound waves from one
medium to another are inter-related
Velocity of sound is directly proportional to the wavelength. Thus, if the velocity of sound doubles when it travels from one medium to another, its wavelength also doubles. The frequency of sound depends upon the source of sound, not the medium of propagation. Hence, it does not change.
suitability of equipment to
measure the speed, frequency and wavelength of a wave in a
solid
suspend metal rod horizontally using clamp stand and rubber band
hit one end with hammer
get frequency app and note peak frequency
measure length of rod
wavelength=length x 2
use frequency and wavelength to calculate speed
suitability of equipment to
measure the speed, frequency and wavelength of a wave in a liquid
set up ripple tank with straight dipper near one side of tank
fasten ruler to one of sides so u see markings
vary the current until see waves with wavelength half as long as tank
count waves form in 10 seconds
use the ruler to estimate the wavelength of waves
use wavelength and frequncy to work out speed
mark 2 points on same edege as ruler use stop watch to mesaure the time for it to go from one mark to the other
ear path
sound waves move along ear canal and hit our eardrum causes vibrate which will transmit through osicles through the semi circular canals and into cochlea which converts into signals
what happens when ultra sound hits medium
partial reflection
Ppl trying to measure spped of sound in air
How could they imrpve the method
Make the distance longer
Cause 50m too short to produce measureable time
Give more accurate result
Describe how hitting the rod causes sound wave to travel along the inside of the rod
Particles at end vunrate in fixed positions which cause neighbouring particles to vibrate
Describe how dolphin use sound waves to see which object closest
Emit and recieve sound reflected from object
Differency in time to recieve echo
Sound recieved in shorter time is closest
Explain how p and s waves show about density and nature of earths core
Where p and s waves detect
P waves arrive before s
Solid cause s waves only travel in solid
Mantle must be solid
Waves refract so mantle gets more dense as u go deeper
No waves
Must be liquid cause no waves go thru liquid
Core must be liquid
R refracted at the boundry
Only p waves
Arrive at different times cause travelled at different speeds
Very centre is solid cause travel faster than those that went tru liquid
