P12 - Wave Properties Flashcards
What is amplitude
The height of a wave crest or trough of a transverse wave from the reset position. The closeness of coils in compression in a longitudinal wave
What is compression?
Squeezing together
What is an echo?
A reflection of sound that can be heard
What are electromagnetic waves?
Electric and magnetic disturbances that transfer energy from one place to another
What is frequency?
The number of waves passing a fixed point every second
What are longitudinal waves?
Waves in which the vibrations are parallel to the direction of energy transfer
What are mechanical waves?
vibrations that travel through a substance
Define Oscillate:
move to and fro about a certain position along a line
What is a Primary Seismic Wave (P-wave)?
Longitudinal waves that push or pull on the material that they move through as they travel through the earth
What is rarefaction?
Stretched apart
What is reflection?
The change of direction of a light ray or wave at a boundary when the ray or wave stays in the incident medium
What is refraction?
The change of direction of a light ray when it passes across a boundary between 2 transparent substances at a non-zero angle
What is a Secondary Seismic Wave (S-wave)?
Transverse waves that shake the earth side to side as they pass through
What are seismic waves?
Seismic waves are waves that travel through the earth, they are produced in an earthquake and spread out from the epicentre
What is wave speed?
The distance travelled by a wave every second
What is transmission/trnasmitted?
A wave passing through a substance
What is a transverse wave?
A wave were the vibration is perpendicular to the direction of energy transfer
What is an ultrasound wave?
Sound wave at a frequency greater than 20,000 Hz (the upper frequency of the human ear)
What is a vibration?
Oscillate rapidly about a certain position
What is a wavelength?
The distance from one wave crest to the next
What is the period of a wave?
The time taken for 2 successive crests (1 wavelength) to pass a fixed point
What is a wave?
A series of oscillations that travel from one place to another, transferring energy
What is a wave crest?
The highest point above the reset point
What is a wave trough?
The lowest point below the reset point
What is the unit for frequency?
Hertz (Hz)
What is the equation for the period of a wave?
T (period) = 1 / f (frequency)
What is the equation for the speed of a wave?
V (speed of wave) = f (frequency) x λ (wavelength)
What is the normal?
The normal is a dotted line drawn perpendicular to the surface of the material, at the point of entry of the light.
What is the law of reflection
The reflected waves move away from the flat barrier at an angle equal to the incident waves (The angle of incidence = the angle of reflection)
What is the angle of incidence?
The angle between the normal and the incident ray
What is the angle of reflection?
The angle between the normal and the reflected ray
What is the incident wave?
The wave travelling towards a barrier or boundary
What is a reflected ray?
A ray of light that has been reflected off a surface
What is a refracted ray?
A ray that travels in another medium and undergoes a change of velocity
What is the equation for the distance of an object detected using sound?
Distance (m) = 1/2 x speed of wave (m/s) x time (s)
Explain how a light wave will be refracted depending on the material that it enters
If a light wave enters a more dense medium, it will slow down as there is more resistance and bend towards the normal. If a wave enters a less dense medium the wave will speed up as there is less resistance and bend away from the normal
How would you demonstrate a mechanical longitudinal wave?
Pulling a slinky forwards and backwards
How would you demonstrate a mechanical transverse wave?
tying 1 end of a rope to a fixed position and moving the other end up and down
What medium do mechanical waves travel through fastest?
Solids
What medium do electromagnetic waves travel through fastest?
a vacuum
What type of wave is a sound wave?
mechanical and longitudinal
What is the pitch of a sound wave?
The frequency
What is the volume (loudness) of a sound wave?
The amplitude
Describe the wave shown in this oscilloscope trace
Loud, high pitched tone
Describe the wave shown in this oscilloscope trace
Loud, Low pitched tone
Describe the wave shown in this oscilloscope trace
Quiet, high pitched tone
Describe the wave shown in this oscilloscope trace
Quiet, low pitched tone
What is an oscilloscope?
An oscilloscope is a machine that shows the wave shape of an electrical signal. When connected to a microphone they can show the wave shapes of sounds.
Explain how we are able to hear noise of people talking loudly in another room
When people in another room are talking, the sound waves travel through the air and then through the walls. The sound waves travel faster when going through walls as the wall is solid, meaning the particles are very close together. The sound waves then travel through the air again and into our ears, down the ear canal. When they reach your eardrums, the sound waves cause it to vibrate. This vibration is transferred to small bones which send signals to your brain about what you are hearing
Explain how ships are able to detect the depth of water.
Ships use a technique called echo sounding. The ships transmit a high frequency sound wave. This is then reflected from the bottom of the ocean and is detected by the ship. The formula “Distance (m) = 1/2 x speed of wave (m/s) x time (s)” is then used to calculate the depth of the water.
What is the speed of sound in water?
1500 m/s
What are 2 medical imaging techniques?
Ultrasound, X-ray
What is the range of human hearing?
20Hz - 20kHz
What is an infrasound wave?
Sound wave at a frequency lower than 20 Hz (the lower frequency of the human ear)
What is an ultrasound scanner?
An ultrasound scanner is an electronic device which makes use of a “transducer” which can be placed on a surface through which it can send pulses of ultrasound waves which can then also be detected - the results can then be shown on a display screen
What are the uses of an ultrasound scanner?
Medical Imaging:
- Looking at organs inside the body
- Looking at damaged ligaments
- Looking at damaged muscles
- Looking at babies inside the womb
Ultrasound scanners can also be used for industrial purposes such as inspecting metals for defects and damage
Why can’t x-rays be used for a baby scan?
X-rays will not show the babies body and limbs, only its bones, meaning you cannot see how some important features of the baby is developing. It can also be damaging to the baby as it is ionising radiation
What happens when an ultrasound wave hits organ tissue?
It is partially reflected
What happens when x-rays hit organ tissue?
They pass straight through
Explain exactly how an ultrasound scanner works
An ultrasound wave pulse from the transducer:
- Is partially reflected by different medium boundaries
- Reflected waves return to the transducer with time taken being monitored
- As the reflected ultrasound waves are detected an image can be produced with the results for that point
- The transducer is then moved around the object to get a full image
What is non-ionising radiation?
A type of low-energy radiation that does not have enough energy to remove an electron from an atom
What is the speed of sound in air?
330 m/s
What is the inner core?
The inner core is the central part of the earth, it is very dense, hot, and it mostly made from solid iron and nickel
What is the outer core?
The section of the earth after the inner core, made of iron and nickel, but liquid
What is the crust?
The outer layer of the earth that is very thin and made mostly of silicon, oxygen, and aluminium
What is the mantle?
A viscous semi-solid below the crust with convection currents circulating within it
What is the atmosphere?
A layer of gases that envelope the crust and the entire earth
What is the shadow zone?
the area of the Earth’s surface where waves are not detected following an earthquake
What is an earthquake?
Forces inside the earth can build up due to tectonic movement and cause layers of rocks to move and break/fracture. The sudden fracture of the rocks releases large amounts of energy, causing a shock wave - which is called a seismic wave. Seismic waves can travel through the earth and across its surface. The study of earthquakes is called seismology.
Describe the properties of P-Waves:
- The P stands for Primary.
- They are longitudinal waves (push-pull) and they are mechanical
- They can travel through liquid and solid so they can travel through the earths core
- They are the fastest seismic wave
- They are bent sharply by changing the density of the material that they’re travelling through
What determines whether a wave requires a medium to travel?
Whether it is mechanical or electromagnetic:
- Mechanical waves require a medium
- Electromagnetic waves do not require a medium
Describe the properties of S-Waves:
- The S stands for secondary
- They are transverse waves (up and down)
- They can only travel through solids
- They are slower than P-waves
- They are bent sharply by changing the density of the material that they are travelling through
Describe the properties of L-Waves:
L-waves (Long Waves), arrive last and cause violent movements on the surface up and down as well as backwards and forwards. They travel more slowly than P-waves or S-waves, and they only happen within the earths crust
What type of seismic waves are detected first?
P-waves because they are the fastest form of seismic wave
What type of seismic waves can travel through the earths mantle?
P-waves, S-waves
What type of seismic waves can travel through the earths outer core??
P-waves
What happens to s and p-waves as they travel deeper into the earths mantle?
Their speed and direction change as the medium they travel through is more dense
What happens to P-waves as they travel across the boundary from the mantle to the outer core?
They refract away from the normal as the density of the medium they travel through is less dense
Use the detection of different seismic waves to provide evidence for the presence of a liquid outer core in the earths surface
P-waves are longitudinal waves meaning that they are able to travel through both solids and liquids. S-waves are transerse waves meaning that they are able to travel through solids but not through liquids. When an earthquake happens in the earths crust, these P-waves and S-waves spread out from the epicentre in all directions. Using a seisometer P-waves can be detected both near the epicentre and on the opposite side of the globe, however S-waves can only be detected nearer to the epicentre. This indicates that in the centre of the earth there is something preventing S-waves passing through but allowing P-waves to travel through. From this it can be concluded that there is a liquid outer core in the Earth’s structure as this would allow P-waves to travel through but not S-waves. Furthermore, the presence of a shadow zone where no waves are detected indicates that the P-waves are being refracted as they pass through a substance with a different density. This indicates that there is a liquid outer core in the Earth’s structure.
What is the equation for snells law?
( Sin(i) / Sin (r) ) = (V₁ / V₂) = (λ₁ / λ₂) = n
i = angle of incidence r = angle of refraction V₁ = speed of wave in 1st medium V₂ = speed of wave in 2nd medium λ₁ = Wavelength in 1st medium λ₂ = Wavelength in 2nd medium n = refractive index
What is an optically denser medium?
A medium in which light travels comparatively slower than the other medium
What is a rarer medium?
A medium in which light travels comparatively faster than the other medium
Label each different wave:
Pink: P-waves
Blue: S-waves
White: L-Waves
Describe how sound waves are produced by a drum and then heard
When the drum is hit, the drum begins to vibrate. The vibrating drum skin causes nearby air particles to vibrate, which in turn causes other nearby air particles to vibrate. These vibrations make up a sound wave, a longitudinal wave. The sound wave travels through the air and towards the persons ear, before travelling down the ear canal towards the tympanic membrane, which vibrates. This vibration is transferred to the brain as signals which creates the sensation of sound
What is the tympanic membrane?
The ear drum
Explain how the human ear can only hear over a certain range of frequencies
The frequency of a wave is reflected by the number of times that it vibrates in a given time. However, there is a limit to the number of times that the eardrum can vibrate in that given time, this is around 20kHz. This limits the range that humans can hear. As humans age the eardrum ages meaning that it cannot vibrate as often, this is why the range of hearing decreases as you get older
Explain the method for investigating waves in a liquid
1) Collect the required apparatus (tray, water, ruler, stopwatch)
2) Measure and record the length of the tray
3) Fill the tray 5cm high full of water
4) Lift 1 end of the tray roughly 3cm up with the other end touching the ground
5) Drop the raised end of the tray and record the time it takes for a wave to travel from 1 end to another
6) Divide the length of the tray (in metres) by the time it took for a wave to travel from 1 end to another (in seconds) to find the wave speed
7) Remove water until it decreases in depth by 1cm
8) Repeat steps 4-7 until the water is 1cm deep
9) If you have time repeat the whole experiment to get a mean average for each result
10) record data in appropriate table/graph
What is an example of a mechanical wave?
Sound wave, Water waves, Seismic waves
What is an example of electromagnetic waves?
Light waves, radio waves, and microwaves
What category of waves are electromagnetic waves?
All electromagnetic waves are transverse waves
What category of waves are mechanical waves?
Mechanical waves can be transverse or longitudinal
What type of waves can be transverse?
Both mechanical and electromagnetic waves can be transverse
What type of waves can be electromagnetic?
Only transverse waves can be electromagnetic
What is the direction of oscillations in a transverse wave?
In a transverse wave, the direction of oscillation is perpendicular to the direction of energy transfer
What is the direction of oscillations in a longitudinal wave?
The oscillations of a longitudinal wave are parallel to the direction energy transfer
What happens if a wave has a larger amplitude?
It carries more energy
Why can you see lighting before you hear the thunder?
Because the speed of light is greater than the speed of sound
What type of wave is shown in the image?
Longitudinal
What type of wave is shown in the image?
Transverse wave
What happens if a wave hits a barrier?
reflection takes place at the barrier, the reflected wave front moves away from the barrier at the same angle as the incident wave front. There is no change in speed or wavelength
What happens when a wave meets a boundary with a different substance?
It may be:
- Totally or partially reflected
- Transmitted through the substance
- Absorbed by the substance
What happens when a wave passes through a substance?
As waves travel through a substance, the amplitude of the waves decreases as the substance absorbs some of the waves’ energy
What is used to detect seimicwaves?
A seismometer
What frequency of sound is most detectable to humans?
3kHz
What can waves not transfer?
Matter
What method is used to detect objects underwater?
echosounding
Which seismic waves are transverse waves?
S-waves
What changes during refraction?
change in speed, direction and wavelength of the waves
