P12- Wave properties Flashcards
Waves transfer energy without transferring what?
matter
What can you use waves for?
transfer information
What happens after a small object is dropped in the water?
The waves travel across the surface but the water does not travel away from the object
What happens in terms of waves to a tuning fork vibrating?
makes sound waves travel through the air away from the tuning fork. The air itself doesn’t travel away from the vibrating object
The oscillations of a transverse wave are what?
perpendicular to the direction in which the waves transfer energy
The oscillations of a longitudinal wave are what?
parallel to the direction in which the waves transfer energy
What are oscillations?
vibrations
All electromagnetic waves are what waves?
transverse waves
What happens if the air itself does travel away from the vibrating object?
It becomes a vacuum
What type of wave is a mechanical wave?
Transverse or longitudinal
How do sound waves work?
When an object vibrates in air, it makes the air around it vibrate as pushes and pulls on the air
What is the amplitude?
Height of wave crest from the middle
Maximum displacement of a point on the wave from its undisturbed position
The bigger the amplitude, the more…
The more energy the waves carry
Longitudinal waves are made up of two things: what are they? [2 marks]
Compression and rarefaction
How would you describe a compression?
region in a longitudinal wave where the particles are close together
How would you describe rarefactions?
a region in a longitudinal wave where the particles are furthest apart.
What is a mechanical wave?
What is a mechanical wave? [3 marks]A wave that can only travel through a medium (substance) and requires particles to move, for instance, sound waves.
What is an electromagnetic wave?
A wave that is able to travel through a vacuum, for instance, light waves and radio waves.
What is the wavelength
distance from one crest to the next crest or from one trough to the next trough.
What is the frequency?
the number of wave crests passing a point in one second.
What are the units of frequency?
Hertz, Hz, waves per second
What is the period of a wave?
the time it takes for one wavelength pass a point.
How can you work out the period of a wave?
period of a wave = 1 / frequency (f)
How can you work out the speed of a wave?
v = fλ
What is the v in v=fλ
wave speed
What unit is wavelength measured in?
metres
In reflection and refraction, what are waves called that are travelling towards a barrier or boundary?
Incident waves
In reflection, what are waves called that are travelling away from a barrier or boundary after reflecting off it?
Reflection waves
In refraction, what are waves called that are travelling away from a barrier or boundary after crossing it?
Refraction waves
What happens in reflection?
Wave hits barrier-> the reflected wavefront moves away from the barrier at same angle to the barrier as the incident wavefront
In reflection, do the reflected waves have any change in speed or wavelength?
No
What happens in refraction?
Wave passes through barrier into a TRANSPARENT or TRANSLUCENT substance- wave changes in speed- causes change in direction
In refraction, do the refracted waves have any change in speed or wavelength?
Yes
When waves meet a boundary with a dif. substance they may be..
Totally or partially reflected; transmitted through the substance; absorbed by the substance.
Why are sound waves caused?
Why are sound waves caused? [2 marks]Sound is caused due to mechanical vibrations in a substance, and travel as a wave.
Are sound waves transverse or longitudinal?
longitudinal
Are sound waves mechanical or electromagnetic?
Mechanical - they cannot travel through a vacuum and need a medium to travel.
How are echoes produced?
How are echoes produced? [1 mark]They are produced when sound waves are reflected off hard, flat surfaces such as walls
How can we investigate waves?
By using: a ripple tank for water waves; a stretched string for waves in a solid; a signal generator and loudspeaker for sound waves.
How can you investigate waves on a string using a freq. generator and oscillator?
1) Adjust the frequency of the oscillator until the string has a single loop.
2) Note the frequency of the oscillator.
3) Measure the length (L) of the loop and calculate the wavelength (λ) of the wave.
4) For a single loop, λ = 2L.
5) Calculate the speed (v) of the waves on the string using v = fλ.
6) Change the frequency of the oscillator to obtain more loops on the string.
7) Calculate further values of λ and v to compare the wave speed.
How can you investigate water waves using a ripple tank?
1) Create plane waves using a ruler. 2)Measure the time taken (t) for a wave to travel from one end of the tank to the other.
3) Measure the distance travelled (s). 4)Calculate the speed of the water waves using v = s/t.
5) Change the frequency of the waves by moving the ruler up and down faster. 6)Calculate further values of v to compare the wave speed.
How can you investigate sound waves using a signal generator and loudspeaker?
1) Observe the loudspeaker cone vibrate when connected to the signal generator. 2)Adjust the oscillator’s frequency & see its effects on the loudspeaker cone’s movement.
3) Adjust the loudspeaker’s volume & see its effects on the loudspeaker cone’s movement.
the pitch of a note depends on the frequency/amplitude of the sound waves.
frequency
the higher the frequency of the waves, the higher/lower the pitch of the sound.
higher
the volume of a sound depends on the frequency/amplitude of the sound waves.
amplitude
the greater the amplitude, the less/more energy the wave carries and the quieter/louder the sound.
more, louder
How do people hear sound in terms of waves?
Sound waves travel through the air.
When they reach the ear, they make the eardrum vibrate
This sends an electrical signal to the brain.
What is the range of frequencies that the human ear can hear?
Between 20 Hz and 20,000 Hz
: the ability to hear higher/medium/lower frequencies declines with age.
higher
What are ultrasound waves?
Sound waves with a frequency higher than 20,000 Hz (too high for a human to be able to hear)
How can you scan using ultrasound?
An ultrasound scanner uses an electronic scanner-transducer- to produce ultrasound waves.
When a wave meets a boundary between two different materials, part of the wave is reflected.
The wave travels back through the material to be detected by the transducer.
The time it takes to reach the transducer can be used to calculate how far away the boundary is.
The results are processed by a computer to give an image.
When a ultrasound wave meets a boundary between two different materials, what happens
part of the wave is reflected.
What happens to the ultrasound waves after it meets a boundary of two different materials?
The wave travels back through the material to be detected by the transducer.
The time it takes to reach the transducer can be used for what?
to calculate how far away the boundary is.
Where are the results processed by in an ultrasound?
processed by a computer to give an image
How can you calculate the distance traveled by an ultrasound pulse?
s = vt (distance traveled equals speed of wave times by time taken)
the depth of the boundary below the surface is equal to/half/double the distance traveled by the ultrasound pulse.
half
Name three uses for ultrasound
medicine-scanning soft tissue such as the eye and the kidney.
scanning unborn babies.
industrial imaging (for instance, for detecting flaws in metal casting)
Why is ultrasound safer than X-ray in medicine?
Ultrasound is non-ionising.
Where are earthquakes generated?
In the Earth’s crust
What is the name of the point that the earthquake originates from?
The focus
What is the name of the closest point on the Earth’s surface to the focus?
The epicentre
What type of waves do an earthquake produce?
Seismic waves
What direction do the seismic waves from an earthquake travel in?
They spread out from the epicentre in every direction.
What are primary seismic waves? p-waves
waves that cause the initial tremors in an earthquake.
What are secondary seismic waves? s-waves
waves that causes the tremors that are produced after the first minute or so.
Are p-waves longitudinal or transverse?
longitudinal
Are s-waves longitudinal or transverse?
transverse
Where does L-waves only travel through?
The Earth’s crust
Why are L-waves slower than p-waves and s-waves?
they cause violent movement in the Earth’s crust
Describe the transitions of P-waves and S-waves between the mantle and the core of the Earth
P-waves refract at the boundary between the mantle and the core, whilst S-waves cannot travel through the core.
Where can p waves travel?
only in the earth’s crust and mantle
Why are p-waves reflected by the earth’s outer core?
It cannot travel through
How is earthquake activity recorded?
recorded by detectors on the surface- seismometers
What are seismometers used for?
to determine where the epicentre of an earthquake is.
How has analysis of seismic waves help scientists?
-allow them to understand structure of earth
What is the structure of the Earth?
liquid inner core (surrounded by)
solid outer core (surrounded by)
mantle (surrounded by)
50km deep crust
