Topic 4- Waves Flashcards
What do waves transfer?
- Energy
- Not matter
How do we know matter doesn’t move in sound and light waves?
Light- particles oscillate up and down
Sound- particles vibrate back and forth
- Ducks (toy) don’t move in water
What is frequency?
How many waves per second
What is wavelength?
Length of a full wave, from peak to peak
What is amplitude?
- The height, equilibrium to the peak/trough
- Loudness of a sound wave/ brightness
What is the period?
How many seconds it takes one complete wave to pass a point.
What is the wave velocity?
- Speed of the wave in a given
direction - changes in different mediums
What is a wavefront?
- Lines that show the peak of a wave that vibrate in unison.
- Equal distance from eachother
What is a longitude wave?
- A wave with areas of compression and rarefaction
- Oscillations occur parallel to the energy movement
- sound waves
What is a transverse wave?
- Wave with a peak and trough
- Oscillations occur perpendicular to the energy movement
- Light/electromagnetic waves
What are two examples of longitudinal waves?
- Sound
- P seismic
What are three examples of transverse waves?
- Electromagnetic (light)
- S seismic
- Water
What are properties of P seismic waves ?
- Can travel through solids and liquid
- Produced by earthquakes
- Faster than S seismic
What are properties of S seismic waves ?
- Slower than P seismic
- Only travel through solids
- More destructive
How do we calculate wave speed?
Wave speed= frequency x wavelength
v=fxλ
Describe how to measure the velocity of sound in air with humans + what are the issues?
1) Place two people across a measured distance (e.g 100m)
2) Person A makes a visual and noise making gesture (e.g loud clap)
3) Person B beings top watch when sees and ends when hears
4) Repeat
5) Human reaction times differ for sound + light
Describe how to measure the velocity of sound in air in microphones?
1)Place 2 microphones 1 metre apart
2)attach to a computerised ossciloscope
3)Make a loud bang at microphone 1
4)M-1 and M-2 will pick up sounds at different times
Describe how to measure the velocity of sound in ripples?
1) Time how long it takes one ripple to move between 2 fixed points
Core Practical: Investigate suitibility of equipmenent to find the frequency, speed and wavelength of a wave in a fluid
1) Record a ripple tank (frequency =no. of waves per second)
2) Place ruler udner ripple tank + use shadows to find wavelength
3) Wave speed = wavelength x frequency
Core Practical: Investigate suitibility of equipmenent to find the frequency, speed and wavelength of a wave in a solid
1) Suspend metal rod with a clamp stand and a rubber band
2) Attach data logger and 2 microphones to each end
3) Start data logger (short time so more precise)
4) Hit one end with hammer
5) Micropohones pick up sound and when it eaches the other end (in data logger) -the time
6) Use distance/time= speed
How to calculate depth from time and speed of a wave?
(time/2)x speed
What is transmission
-Wave passes through an object without being absorbed
What is reflection?
-Wave bounces off the boundry between 2 different mediums
-Angle of incidence= Angle of reflection
What is refraction?
1) An wave speeds up/ slows down when entering a materil with a different density
2) To keep the same frequency, its wavelength shorterns (all inter-related)
incidence ray, refracted ray and emergant ray
Do sound waves speed up or slow down in denser mediums?
-speed up
-Longitudinal, closer particles
opposite for light
If a wave slows down it bends which way when refracted?
Towards the normal line (90 degrees to object)
e.g light in denser, sound in less dense
How do objects interact with different wavelengths?
-differently
-some absob/ transmit/ reflect
-e.g why we see colour
Parts of the human ear?
1) Ear canal
2) Ear drum
3) Ossicles (3 small bones)
4) semicircular canals
5) Cochlea
6) Auditory nerve
How do humans hear?
-Sound is filtered into + travels along ear canal
-Cuases ear drum to vibrate
-Osiccles and semicircular canals transmit to cochlea
-Cochlea converts into electrical signal
-Across auditory nerve to brain to be interprited
e.g higher frequency = higher pitch
Avg hearing range of humans?
20 Hz—>20,000 Hz
decreases when older due to wear + tear
What is ultrasound?
sound with greater frequency than 20,000 Hz
What is Infrasound?
sound with lower frequency than 20 Hz
What can we use ultrasound for?
-Foetal scanning
-Sonar
-Industry poroducts
-Medical e.g kindey stone breaking
How does feotal scanny work?
-Use an emitter + reciever on stomach
-Reflected when reach boundry
-processed into 3D image
safer than x-ray as less energetic (lower frequency), non ionising
How does ultrasound work for industry work?
-Air in any cracks
-Ulttrasound is reflected too ealy
-reflected from boundry of product to air
How does ultrasound work for sonar work?
- Ultrasound emitted then reflected back t boundry to other density objects
How does ultrasound work for kidney stones work?
-vibrates into smaller peices
non ionising
How is infrasound used for discorvering earth’s core?
-P seismic waves travel through liquid + solid
-S seimsic only though solid
-S seismic found on same half of Earth as earthquake, wherease P everywhere + increased refraction
-Suggests their is liquid outer core
-Region where no waves are detected due to gradual refractions through mantle + liquid outer core
What measures seismic waves?
seismometer
