Topic 4 Flashcards
Done except for few specpoints
4.1
What is a wave
Method of transferring:
-E & info
-From a source
-w/o matter
4.2
Define the term compression
Areas in the wave where the particles are close together
4.2
Define the term rarefraction
Areas in the wave where the particles are far apart
4.2
Describe evidence that with water and sound waves it is the wave and not the water or air itself that travels
-Water/air molecules oscillate in place as E passes through
-Molecules themselves don’t travel w/ wave
4.3
Define the term frequency. What is it measured in?
-No. of waves passing a given point/s
-Hz (Hertz)
4.3
What is the equation for working out the frequency of a wave?
f=1/T
4.3
Define the term wavelength
What is it measured in?
-Distance from peak to peak or trough to trough
-m (metres)
4.4
Define the term amplitude
What is it measured in?
-Distance from rest position to peak or trough
-m (metres)
4.4
Define the term period
What is it measured in?
-t for 1 wave to pass given point
-s (seconds)
4.4
What is the equation for working out the time period of a wave?
T=1/f
4.4
Define the term wave speed. What is it measured in?
Total distance covered by wave in given time period
(m/s)
4.5
Compare transverse and longitudinal waves
Transverse - Oscillation of particles PERPENDICULAR to direction of wave
WHEREAS
Longitudinal - Oscillation of particles PARALLEL to direction of wave
4.5
State 4 examples of transverse waves
-Sea/water waves
-Light waves
-Other electromagnetic waves
-Some seismic waves
4.5
State 2 examples of longitudinal waves
-Sound waves
-Some seismic waves
4.6
State 2 equations for wave speed (velocity)
State their units
Wave speed(m/s) = frequency(Hz) × wavelength(m)
v=f×λ
Wave speed(m/s) = distance(m) ÷ time(s)
v=x/t
4.7
Describe how to measure the velocity of sound in ripples on water surfaces
-Use ripple tank w/ vibrating bar
-Bar connected to power pack
-Vibrates -> waves on water surface
-Lamp above ripple tank
-White paper under w/ ruler alongside
-Light shines thru water -> image of waves on paper
-Record w/ phone
-Freeze image & measure λ
-Find f: record timer + waves & watch in slow motion
-Count no. of waves passing point in 1 sec
-v=f×λ
4.7
Describe how to measure the velocity of sound in ripples on water surfaces
-Select wave
-Measure tank length
-Measure t takes to move tank length
-s=d/t
4.8P
The sound wave released from a ship took 0.12 seconds to return. The speed of sound in water is 1500 m/s. What was the depth of the sea?
90m
Define the term oscillation
VIBRATION of particles back and forth around an EQUILIBRIUM point
What are the colours of visible light?
Red
Orange
Yellow
Green
Blue
Indigo
Violet
4.9P
Define the term absorbed
When a wave is taken in by a medium
4.9P
Define the term transmitted
When a wave passes all the way through a medium
4.9P
Define the term reflected
When a wave is cast back from a different medium
4.9P
What is the normal?
Perpendicular line to the interface
4.9P
What is the interface?
Boundary between two media e.g. glass & air
4.9P
What is an incident ray?
Ray that approaches the interface
4.9P
What is a refracted ray?
Ray that has been bent entering new medium
4.9P
Define the term medium
Material through which waves are transmitted
4.9P
Define the term refraction
The bending of waves when they change speed
4.10PH
Which way will a wave bend/refract if it enters a denser medium? Describe the angle of refraction in relation to the angle of incidence
-Slows down so TOWARDS normal
-<r less than <i
4.10PH
Which way will a wave bend/refract if it enters a rarer medium? Describe the angle of refraction in relation to the angle of incidence
-Speeds up so AWAY from the normal
-<r greater than <i
4.10PH
An incident ray enters a medium and refracts. State 2 factors that will affect the angle of the refracted ray.
-The speed the ray travels in the two media
-The angle of the ray hitting the interface
4.10PH
Describe what will happen when a light ray enters and leaves a glass block
-When incident ray hits interface slows down & bends TOWARDS normal
-When leaves glass bends AWAY from normal
-PARALLEL to original incident ray
4.11
How do different substances absorb, reflect, refract and transmit waves?
In ways that vary w/ λ
4.12PH
Explain why the human ear only works over a limited frequency range
-Ossicle size = too small
-Limited hair cell lengths
4.12PH
Describe how the human ear works
[6 marks]
-Ear detects sound
-Pinna funnels sound waves into ear canal
-Sound waves travel along ear canal and cause ear drum to vibrate
-Ossicles (3 tiny bones) transmit vibrations to cochlea
-Cochlea generates an electrical signal
-Auditory nerve transmits electrical signal to brain
4.13PH
What is ultrasound?
Sounds with frequencies greater than 20,000 Hz
4.14PH
What is infrasound?
Sounds with frequencies less than 20 Hz
4.15PH
Explain why ultrasound is used for foetal scanning instead of x-rays
X-rays EMIT radiation -> can harm baby
4.15P
State 4 uses of ultrasound
-Jewellery cleaning
-Teeth cleaning
-Foetal scanning
-Sonar
4.15P
State 2 uses of infrared sound
-Exploration of Earth’s core
-Communication by animals
4.15P
Describe how sonar works
-Boat sends ultrasound into water
-Ultrasound reflects from sea bed
-Boat detects echo
-Measures time between sending and receiving wave
-x=v×t/2 to figure out depth
Explain what states of matter sound waves would travel the fastest in
-Solids & liquids
-Particles closer together
-Less E dissipated
Which colour travels the fastest? Describe its wavelength
Red (longest wavelength)
Describe the relationship between wavelength and speed
-Directly proportional
-As waveLENGTH increases, speed increases
Which waves travel fastest, P waves or S waves? Explain both
-P waves
-Push and pull motion between particles transfers energy forward very quickly
-In S waves, energy transferred forward slower because transverse
What media can P waves travel through?
Solids & liquids
What media can S waves travel through?
Solids
What type of wave is a P wave?
Longitudinal
What type of wave is an S wave?
Transverse wave
Why are P waves and S waves constantly bending as they travel through the earth?
Rock density increases -> refract
