11.1 + 11.2 waves Flashcards
What waves do earth quakes produce and what type are they?
Primary p waves= longitudinal
S waves= transverse seismic
What are progressive waves
- all progressive waves transfer energy from one place to another (through a medium (matter/ vacuum) ), but not matter
- both transverse and longitudinal are progressive
How does a wave work if it doesn’t transfer matter
In longtidunal ?
-Particles in the medium will move from original equilibrium position to a new position
-Then the particles in the medium exert forces on Esch other, so a displaced particle will experience a RESTORING FORCE from neighbours and is PULLED BACK TO ITS ORIGINAL POSITION
(Like water example)
2) collisions happen which provide restoring forces
Difference and similarities between transverse and longtidunal waves?
- Both are progressive waves , that transfer energy without transferring matter
- however transverse waves oscillate at 90° to direction of energy transfer/ WAVE
- with peaks and troughs
- whereas longitudinal waves socialite parallel to direction of energy transfer/ WAVE
- with compressions and rarefactions
Longitudinal waves need a medium and CANT BE POLARISED
Time period And frequency?
What equation
- time period = time taken for one wave to oscillate
- frequency = number of wavelengths passing a point per second
F = 1/ t
Because if it take 4 sec for 1 wave to go, then 0.25 waves per second , or 1/ time period = 1/4= 0.25
What types of transverse vs longtidunal
Transverse = EM, S waves , water wave, rope Longitudinal = sound, ultrasound, p waves
What is phase difference
What does being in phase mean
What is one whole wavelength again
What is antiphase
1) describes the difference between displacements of particles along a wave, or difference of displacements in different waves .
2) being In phase is when particles oscillate perfectly in step of each other (reach MAXIMUM DISPLACEMENT AT SAME TIME= PHASE), phase difference is 0.
3) one whole wavelength is 2 pi
4) antiphase is when one particle reaches maximum displacement and other minimum. This is phase difference of 1 pi, odd integer of pi
Formula for phase difference
Phase difference = x(distance)/ wavelentgh x 360
This shows if distance between two particles are same as wavelength then phase difference is 360
What point on a graph is a wave at its maximum velocity
- acceleration ?
Middle, as it’s about up or down, the rest of either slowing down or stationary
- minimum at top
- max acceleration at top and least at middle
How to use oscilloscope to determine wave frequency
Use each box and find the time it holds,
Then you get time periods
Then you can get frequency from that
- as thus us equal to the sound frequency, you have it
Why does sound move faster in denser medium
Denser medium = more particles closer together
- this means particles don’t need to be displaced as far to interact with neighbouring particles
- energy is transferred faster in dense as a result
Displacement key words ?
distance and DIRECTION OF a particle (vibrating) on a wave from rest
What happens if waves meet at same frequency with time moving forward in relation to phase?
Coherent = phase
Otherwise they will change phase difference with time , cycling from 0 and 2pi
Why we use radians rather than degrees
- used to think 360 days in a hesr, so assumed 360° in a revolution
- physicists use the fact that a radius will be its revolution if multiplied by 2pi r
So pi used, and 2pi radians is one revolution
What are technically the two types of waves
1) mechanical and EM waves
Longitudinal and transverse are thus just modes of vibration .
Mechanical can be both transverse / longitudinal, EM only transverse
