Waves 6.1 Flashcards
All wavesare either:
- transverse
- longitudinal
what type of wave is ripples on the surface of the water
-transverse wave
what type of wave are sound waves travelling in air
-longitudinal waves
all waves transfer energy from one place to another
how do ripples on the surface of water transfer energy
how do sound waves transfer energy
- ripples transfer kinetic energy
- sound waves transfer sound energy
the waves move up and down
what do scientists call these movements
-oscillations
what are the oscillations like in transverse waves
in transverse waves, the oscillations are perpendicular to the direction of energy transfer.
in transverse waves
oscillations are up and down but the direction of energy transfer is sideways
a good example of longitudinal waves are sound waves
sound waves travel as particles in the air move from side to side.
there are regions where the particles are very close together and scientists call these regions compressions.
in between the compressions, there are regions where the particles are spaced out, these regions are called rarefactions.
in longitudinal waves the oscillations are parallel to the direction of energy transfer.
aside from that difference, there is also another difference between transverse and logitudinal waves all longitduinal waves require a medium to travel
give examples of a mediumf
air
liquid
solid
do transverse waves require a medium
no, not all transverse waves require a medium
for both ripples on a water surface and sound waves that travel through air its the wave that travels and not the water or the air.
the air particle or water particle does not travel through the medium, it moves side to side with the oscillations (in the sound wave longtudinal) or it moves up and down with the oscillations (in a ripple on the surface of water transverse)
free science lessons exercise: what type of waves are water waves and what type of energy is transferred
- water waves are transverse waves
- water waves transfer kinetic energy
free science lessons exercise: what type of waves are sound waves and what type of energy is transferred in sound waves
sound waves are longitudinal waves
-sound waves transfer sound energy
free science lessons exercise: correct the statement
the movement of the transverse wave sideways is called an oscillation
correct statement- movement of the transverse wave up and down is called oscillation
correct the statement
in transverse waves the oscillations are parallel to the direction of energy transfer
-correct statement: in transverse waves the oscillations are perpendicular to the direction of energy transferred
correct the statement: in the transverse wave above, the direction of energy transfer is up and down
correct statement- in a transverse wave the direction of energy transfer is sideways from left hand side to right hand side
correct the statement: water waves are longitudinal
correct statement: water waves are transverse waves
fill in the gaps
in transverse waves the oscillations are ———– to the direction of energy transfer
perpendicular means at ———- angles
in transverse waves the oscillations are perpendicular to the direction of energy transfer
perpendicular means at right angles
in compression, the particles are
select the right option
-further apart
-closer together
in compression, particles are closer together
in rarefaction particles are:
select right option
-further apart
-closer together
in rarefaction particles are further apart
in longitudinal waves, how can you link direction of energy transfer and direction of oscillations
iin longitudinal waves, oscillations are parallel to direction of energy transfer.
what is another difference between longitudinal and transverse waves
-longitudinal waves travel through a medium air , liquid or solid
not all transverse waves require a medium to travel.
an example is that, light is a transverse wave and it travels through a vacuum( no particles)
in both water waves and sound waves in air its the wave that travels and not…
the water or air.
water or air particles do not travel through the medium, they move with the oscillations up and down (transverse) or sideways from left to right (longitudinal)
what are compressions,
in sound waves or other longitudinal waves there are regions where the particles are very close together. these regions are known as compressions
what are rarefactions
in between compressions, these are regions where particles are more spaced out, they are further apart
-Describe the differences between
transverse and longitudinal waves and give
examples
transverse waves- examples are water waves and ripples , light waves
wave on a string
electromagnetic waves
in transverse waves, the oscillations are perpendicular to the direction of energy transfer,
the oscillations are up and down whereas the direction of energy transfer is sideways from left hand side to right hand side.
transverse waves do not require a medium to travel through for example light waves are transverse but travel through a vacuum.
longitudinal waves examples include, sound waves in air (ultrasound)
some seismic waves
in longitudinal waves, the oscillations are parallel to the direction of energy transfer.
all longitudinal waves travel through a medium eg air, liquids and solids
definition of amplitude
maximum displacement of a point on a wave away from its undisturbed position
definition of wavelength
wavelength of a wave is a distance from a point on one wave to the equivalent point on a adjacent wave
symbol of wavelength is greek lambda
how do you measure wavelength on longitudinal waves
measure from one compression to the next compression or from one rarefaction to the next rarefaction
definition of frequency
number of waves passing through a point each second
1HZ= 1 wave per second
to find the frequency from a diagram count number of complete waves and divide by the number of seconds to tell you the number of waves per second/
definition of period
the period is the time (in seconds) for one wave to pass a point.
period can be calculated by
1/ frequency
definition of wavespeed
the wavespeed is the speed at which the wave moves through the medium (the speed at which energy is transferred)
equation for wavespeed
frequency x wavelength
Hz x m =m/s
method to measure speed of soundwaves in air
two people are separated by a distance of 500 m
person A holds the cymbals person B holds a timer
person B starts timing when they see person A clash the cymbals together
Person B stops timing when they hear sound of cymbals crashing
the speed of the sound waves can be calculated by dividing the distance travelled by the time taken
what are some problems with the experiment of measuring the speed of sound waves in air
-every person has a different reaction time
it takes a fraction of a second between seeing the cymbals and starting the timer it also takes a fraction of a second before hearing the sound of the cymbals and stopping the timer
we can reduce this error by having a large number of observers with timers
we can take all the results and discard any that are anomolous
we can also calculate a mean value
it takes a very short time between seeing the cymbals crash and hearing the sound, that makes it difficult to press the timer at the correct times. we can reduce this error by increasing the distance between person A and person B. the longer the distance the longer the time, that makes it easier to start and stop the timer at the correct times.
required practical ripple tank
we are measuring the wavelength frequency and speed of water waves
give definitions of all three
wavelength- distance from one point on a wave to the equivalent point on an adjacent wave
frequency- number of waves passing through a point each second
1hz= 1 wave per second
wavespeed- speed at which the wave moves through the medium or speed at which energy is transferred
remember water waves transfer kinetic energy
equation= wavespeed= frequency x wavelength
what does a ripple tank do/ why is it used
a ripple tank is used to determine the features of water waves
how does the experiment work
a ripple tank is a shallow tray of water and in the water is a vibrating bar which is connected to a power pack
when the bar vibrates it creates waves across the surface of the water
above the ripple tank is a lamp and below the ripple tank is a sheet of white paper
when light shines through the water, it produces an image of the waves on the paper
how do we measure the wavelength using a ripple tank wavelength definition ( distance from one point on a wave to the equivalent point on an adjacent wave)
to measure wavelength place a ruler on the paper. freeze the image of the waves.
measure the distance between one wave and 10 waves further (a total of ten wavelengths)
to find one wavelength divide this by ten
how do you measure frequency using ripple tank experiment
frequency= number of waves passing a point each second
1hz= 1 wave per second
place a timer next to paper and count number of waves passing a point in 10 seconds. now divide the number of waves by 10 to calculate number of waves passing a point each second. ( counting number of waves passing the point in ten seconds gives more accurate results than measuring for one second)
we can make this easier by recording this and watching it in slow motion, in this case you would need to also record the timer as well as the waves.
how to determine wavespeed from ripple tank experiment
we already know wavelength and frequency of waves so we can use this to determine the wavespeed by multiplying the wavelength and the frequency.
wavespeed m/s= frequency hz x wavelength m
whats another way to determine wavespeed using ripple tank experiment, other than using the wavespeed equation
- select a wave
-measure time taken for wave to move the length of the tank
divide the distance travelled by the wave by the time taken for it to move the length of the tank.
we might get two slightly differnet results using these two methods to determine wavespeed of the water waves
what is this due to
-measurement errors eg timing
describe apparatus of required practical for waves in a solid
we have a string with one attached to a vibration generator.
we have a hanging mass at the other end of the string
the mass keeps the string taut
the vibration generator is attached to a signal generator
the signal generator allows us to change the frequency of vibration of the string
when we turn on the power, the string vibrates
at a certain frequency we produce a standing wave
what is a standing wave caused by
effect of resonance.
where do we find standing waves
in stringed instruments such as a guitar
how do we measure wavelength of a standing wave
use a ruler
measure total length of standing wave from vibration generator to wooden bridge.
we can use the wavelength to calculate the speed of the wave
use the wave equation
wavespeed m/s= frequency Hz x wavelength m
read the frequency from the signal generator.
what happens if we increase the frequency
the standing wave changes
we get three halfwavelengths
how do we calculate wavelength of the changed standing wave ( increased frequency causes standing wave to change)
to calculate wavelength divide total length from wooden bridge to vibration generator by number of halfwavelengths and then multiply by 2
analysis
wavespeed of the string does not depend on frequency or wavelength
the wavespeed depends on the tautness of the string and the mass/cm.
to calculate wavelength of standing wave
divide total length (from wooden bridge to vibration generator) by number of half wavelengths and then multiply by 2.
what is the purpose of the mass on the string
to keep the string taut
what is the purpose of the signal generator
it sets the frequency of the vibration generator
what type of musical instruments do we find standing waves in
guitar /stringed instruments
recall wavespeed equation
-wavespeed m/s= frequency hz x wavelength metres
what two factors affect speed of wave in a piece of string
tautness of the string
mass/cm of the string
how could the student change the tautness of the string
add a heavier mass increasing the mass would increase tautness of the string
apart from changing the frequency how could the equipment be changed to adjust the standing wave
by changing the position of the wooden bridge.as we move the wooden bridge closer or further from the vibration generator. the standing wave will change
what happens when a wave hits a boundary with a different material for example glass
-the wave could simply be transmitted through the material
in certain cases, waves can change direction when they pass from one material to another (refraction)
energy of wave could be absorbed by material, the wave may then not pass through material at all
wave may simply be reflected off surface of the material
what is refraction
when waves can change direction when passing from one material to another.
the surface of a material can:
- transmit
- absorb or
- reflect waves
transmission, absorption or reflection depends on the material and the wavelength of the wave
depends on both material and the wavelength of the wave
what is the dotted line at right angles to the surface of the mirror called
a normal
what is the angle between the incident ray and the normal called
angle of incidence
key fact:
angle of reflection= angle of incidence
to find a position of a reflected image first draw a ray diagram and …
draw a normal at right angle to surface of mirror and draw the reflected ray. remember= angle of reflection= angle of incidence
now draw another normal and draw another reflected ray
extend both reflected rays and where the two lines meet tells us the new position of the image.
required practical- reflection and refraction of light we need a raybox, a lens and a slit this produces a narrow ray of light
why do we need a slit- to produce a narrow ray of light
rayboxes can get hot, must switch them off when not in use
the practical isnt done with a laser because that could be more dangerous so a raybox is safer
1) first, take a piece of A3 paper and draw a straight line down the centre using a ruler
2) use a protactor to draw a line at right angles. this is the normal so its labelled N
3) place a glass block agaisnt the straight line going down the paper so that the normal is near the centre of the block
4)now draw around the glass block. turn off all the lights in the room
5) use a raybox to direct a ray of light so it hits the block at the normal. this is the incident ray
6) the angle between the incident ray and the normal is the angle of incidence.
7) to change the angle of incidence adjust the raybox at a certain angle we can see the ray reflect from the surface of the block. we can also see another ray leaving the block from the opposite side. this is the transmitted ray.
8)we can mark the path of the incident ray and the reflected ray with crosses also mark the transmitted ray.
9) trun on room lights and switch off raybox
10)remove glass block
11) draw in reflected ray and incident ray
draw in the transmitted ray so that it meets position of the block and draw a line to show path of transmitted ray through glass block.
12) use protactor to measure angles
13) the angle of refraction is the angle between the normal and the path of the transmitted ray through the block
14) repeat whole experiment using a block made from a different material e.g plastic such as perspex
conclusion
angle of incidence and reflection are same for both glass and perspex because the angle of incidence and reflection do not depend on the material
angle of refraction for perspex will be different than that of glass block because angle of refraction is different for different materials.
how could the angle of relection angle of incidence and angle of refraction be different using perspex block than using glass
The angle of incidence and angle of reflection do not depend on the material. We set the angle of
incidence using the ray box. The angle of reflection will always be the same as the angle of incidence.
However, the angle of refraction does depend on the material. We will find that the angle of refraction
will not necessarily be the same for different materials.
angle of refraction is different for different materials
required practical questions
in the practical a raybox lens and split is used why is this used rather than a bulb
because the split allows a narrow ray of light to pass through
what is a safety issue with the equipment and how could the risk be reduced
the raybox can get very hot so we must switch it off when not in use
why do the lights need to be turned off
light rays from a raybox can be very faint so turning off the lights makes them easier to see
what is the angle between the incident ray and the normal called
angle of incidence
what is the link between the angle of incidence and the angle of reflection
they are equal to each other
how would the angle of incidence, angle of reflection and angle of refraction compare between the glass block and the perspex block
the angle of incidence and the angle of reflection would be the same for both the glass block and the perspex block because angle of incidence and angle of reflection do not depend on the material. however, the angle of refraction would change for the perspex block because the angle of refraction depends on the material
sound waves-
sound is a longitudinal wave
when sound waves move through the air the air particles vibrate from side to side
the vibrations can pass from one medium to another for example from an air to a solid
what is one of the key parts of a microphone
the paper cone when sound waves hit the cone, this causes it to vibrate
the microphone converts these vibrations to electrical signals
human ear sound waves in the air are funelled into the ear where they hit the eardrum
what is the eardrum
a thin membrane
the sound waves cause the eardrum and other parts of the ear to vibrate
what does this cause
sensation of sound
sound waves in the air can trigger vibrations in solids but
it only works over a limited range of frequencies
normal human hearing
frequency range
20hz to 20,000 hz
frequencies outside of the range are not able to cause the eardrum to vibrate
when waves move from one medium to another their speed can change
example:
sound waves travel much faster in solids then in gases
because the particles in a solid are much closer together so the vibrations can pass more easily between them
wavespeed and wavelength are directly proportional to one another so when the wavespeed changes as the wave passes from one medium to another,
the wavelength also changes
frequency does not change when waves pass through a medium why
waves would have been created or destroyed at the boundary and that is not possible.
the features of sound waves can be viewed by connecting a microphone to a ..
cathode ray oscilloscope
the problem with using a cathode ray oscilloscope is that it presents sound waves as if they were transverse waves.
why is this a problem
because sound waves are longitudinal
high frequency sound has a
high or low pitch
high pitch
low frequency sound has a high or low pitch
a low pitch
small amplitude produces a
quiet or lound sound
a quiet sound
large amplitude
loud sound
sound waves can only move through a medium eg air or a solid
because sound waves move by particles vibrating. sound waves cannot pass through a vacuum because there are no particles
just like light, sound waves can be reflected
reflected sound waves are called
echoes
sound waves in air are always longitudinal waves
true or false
true-
what happens to air particles when sound waves travel through air
air particles vibrate from side to side because in longitdudinal waves, osciilations are parallel to direction of energy transfer.
how do sound waves pass from one medium to another in microphones
sound waves hit the paper cone causing cone to vibrate from side to side. microphone converts vibrations to electrical signals by the electrical circuit of the microphone
how do sound waves pass from one medium to another in ears
the sound waves are funelled into the ear where they hit the eardrum, causing it to vibrate from side to side this causes other parts of the ear to vibrate and the brain interprets this as sound
louder sounds have a greater
amplitude or frequency
than quiter sounds
choose correct option amplitude or frequency
louder sounds have a higher amplitude than quieter sounds
high pitched sounds have a greater
amplitude or frequency
than low pitched sounds
high pitched sounds have a greater fequency than low pitched sounds
what do we call reflected sound waves
a echo
explain why sound waves need a medium to travek through and cnnot travel through a vacuum
sound waves move by vibrating particles there are no particles in a vacuum
what is the definition of ultrasound
ultrasound is sound waves witha frequency higher than the upper limit of the human hearing
the frequency of ultrasound
atleast 20,000 hz
what is a key feature of ultrasound
ultrasound partially reflects at the boundary between two different densities
how can we calculate distance between a probe and a kidney
if we know the time it takes for the ultrasound pulse to leave the probe bounce off the kidney and then be detected by the probe, we can calculate the distance between the probe and the kidney
what can ultrasound scanners produce
images of the internal organs such as kidney and the heart it works for any organ thats not surrounded by a bone. we can also use ultrasound to produce images of a feotus ultrasound is safer than xrays because it does not cause mutations and it does not increase the risk of cancer
ultrasound is also used in industrial imaging
ultrasound can be used to scan pipes. it can detect hidden defects or detect problems with weld.
to determine the distance using ultrasound use equation below
speed= distance x time
a ship is using ultrasound to dtermine distance of seabed an utrasound pulse is emitted
it takes 1.2 seconds for reflected pulse to return to ship.
calculate depth of seabed
the speed of ultrasound in water is 1600m/s
distance= speed x time
1600 x 1.2= 1920m
thats the distance that the ultrasound pulse has travel from ship to seabed and back to the ship
to work out the depth of the seabed divide by 2
internal structure of Earth
- outside of Earth is a solid crust the crust is very thin with a maximum depth of 50km
- under crust is mantle mantle is a solid parts of upper mantle can flow very very slowly but mantle is still considered solid
- outer core is liquid
- inner core is a solid
why can scientists not directly observe stucture of interior of Earth
Earths crust has a maximum depth of 50km but the deepest mines only go to a depth of a few kilometeres into the crust
why does an earthquake happen
due to a sudden movement of the tectonic plates in the earth’s crust
this causses seismic waves which carry energy away from the earthquake
the seismic waves pass through the Earth and be detected in different countries by seismometers
what do patterns of these seismic waves give us information about
interior of the Earth
two types of seismic waves
p waves
s waves
what are p waves
p waves are longitudinal waves that can pass through both solids and liquids
p waves travel faster than s waves
what are s waves
- transverse waves
- s waves can only travel through solids
why do seismic waves travel in curved paths
due to the density changes in the Earth
there are large parts of the Earth where no s waves can be detected
what are these called
s wave shadow zone
what causes the s wave shadow zone
s waves cannot pass through liquid
this tells scientists that Earth must contain a liquid core
there are large parts of the Earth where p waves cannot be detected
these are called p wave shadow zones
what causes p wave shadow zones
due to the fact that p waves travel faster in solids than in liquids this means p waves slow down as they enter liquid outer core causing them to refract
they also refract when they leave the outer core
this also confirms that outer core is a liquid
how can scientists show that earth contains a solid inner core
faint p waves detected in p wave shadow zone
how have scientists worked out thickness of crust and mantle and outer and inner cores
measured seismic waves from thousands of Earthquakes
fill in the gaps.
scientists have worked out the internal structure of Earth using ——-. when an earthquake takes place, there is a sudden movement between Earth’s ——- plates. seismic waves now carry energy away from from the earthquake. these waves pass through earth and are detected by ——– in different countries. the pattern of seismic waves gives us information on the Earth’s ——-. there are two types of seismic waves. p waves are ———– and can pass through both —— and liquids. s waves are —— and can only pass through solids. s waves travel more ——– than p waves.
Scientists have worked out the internal structure of the Earth using earthquakes. When an earthquake
takes place, there is a sudden movement between the Earth’s tectonic plates. Seismic waves now
carry energy away from the earthquake. These waves pass through the Earth and are then detected by
seismometers in different countries. The pattern of the seismic waves gives us information about the
Earth’s interior. There are two types of seismic waves. P waves are longitudinal and can pass through
both solids and liquids. S waves are transverse and can only pass through solids. S waves travel more
slowly than P waves.
