Topic 3 - Waves Flashcards
All waves …
Transfer energy from one palce to another .
In transverse waves ,.
oscillations are perpendicular to the direction of energy transfer . (oscillates up and down and direction of energy side ways ).
exmpale ripples
Longitiudinal waves .
examples - sound waves these rtravel a particles move from side to side ,
-oscillaitons parallel to energy transfer (side to side waves move )
-A longitudinal wave alsoo travels a medium to travel in , air liquid , solid .
In contrast with Transverse waves , these do not all require a medium .
Its the WAVE that travels not THE WATER .
.
What is amplitude ?
Amplitude of wave is the furthest poitnt a wave vibrates from its undistrubed position
(lin ein middle ).
What is wavelength ?
Wavelength of a line is the distance froma point on one wave to same point on the adjacent wave .
(Symbol for wavelength remeemberr )
-wavelength difficult for longitudinal wave usualy give TRANSVERSE wave .
What is the frequency ?
Frequency is th enumber of waves passing per second .
Unit of frequency is Hhz
1Hz is one wave per second .
Frequency figure out - COUNT THE TOP OF ONE WAVE TO ANOTHER THATS ONE WAVE .
What is the period ?
Time in seconds for one wave to pass a point .
Period (s) = 1/Frequency(Hz)
What is the first stage of waves in a solid RQP ?
String attached to a vibration generator .
- Othe end hanging mass , keeps string taut .
- Vibraiton geenrator attached to signal generator allows us to change frequency of vibrations of strong .
What is the second stage of waves in a solid RQP ?
-When we turn it on , the string vibrate s, difficult to see bibrations but as the certain freqeucny we see a stadning wave .
Standing wave is due to an effetc clled resoannce .
What is the third stage of waves in a solid RQP ?
Measure the wavelength of the sanding wave using a ruelr , Measure legnth of stadnign wave from woodern bridge to vibration geenrator .
What is the fourth stage of waves in a solid RQP ?
Calculate spped of wave usign euqatin
Wavespeed = Frequency (Hz) *Wavelength (m)
What happens if we increase wave length
Get half ways
calculate wave length by
Dividing total length of wave / by number of half wave lengths and *2
So what does the waveseped of the string dpeend on ?
It does not depend on frequency or wavelegth but the taughtness of string and mass per cm .
WHat does a ripple tank do ?
Observe fetaures of water aves .
First stage of ripple tank rqp.
1.Shallow tray of water with a vibrating bar ,
Bar is connected to a power pack .
Second stage of ripple tank rqp.
When bar vibrates , it creates waves across the surface of the water .
Third stage of ripple tank rqp.
Above the ripple ank , therre is a lmap nad below the tank a sheet of white paper .
-When light shines thorugh the water , it porcduces an image of avees on paper .
(Easiest way is to record on mobile phone as we see at different speeds and freeze image )
Fourth stage of ripple tank rqp.
Measure the wavelength ith a rule on paper . Then freeze image of wave .
-Now measure disartanc ebetween one waves and ten waves furhter (10 wavelenths )
to find wavlength divide this by tne .
fith stage of ripple tank rqp.
-To find frequency , put a timer next to paper and cont number of waves passing a point in one seocnd . ( count number of waves passing in seconds and idvide by tne ) good watch in slow motion .
sixth stage of ripple tank rqp.
Work out wavespeed
wavsepepd (m/s) = frequency (hz) *wavelength
or mesure wavespeed by slecting a ave and how long it takes to pass length of rippel tank then work out speed by distance over time .
CAN GET INACCURACIES when trying to time .
What happens when one wave moves into another mediium ?
-it can change direction and change speed .
What happens when lihgt passes from air into glss ?
- velcoity of light decreases (ligh wave slows down )
- casuign wave to change direction
- when waves slow down , bend toward normal
- wave leaves the galss back into air velcoity increases as light wave sppeeds up
- bedning aaway from normla
more about waves enetering a medium ?
- Wave fronts - imaginery line connects that connect waves all at the same point
- as light eneers the glass ,the wavefronts get clsoer , so wavelength gets smaller , waves change direction towards normal refracting .
Mechanical waves
–need a substance / particles to oscillate for the wave to pass thorugh .
(sounddw aves , earthquake and water waves )
Electromagnetic eaves
-can pass through even when there are np a[rticle s(ina vaccum) as as when there are [articles alaways transvere (microwaves xrays and uv light )
What are electromagneitc waves ?
- transverse waves
- Transfer enegry fromt he source of tge wave to an absorber .
More about electromagnetic eaves .
- On the red end of the epsectrum , waves have a lower frequency and longer eavelength . #
- On the violet end fo the spectrum higher frequency and shorter wavelength .
List he em wabes from lwoest freqeucny to highest frequenxy .
-lowest freqquency highest wavlength radio then till gamam which has highest frequency and hsortest wavelength .
radiO Waves Microwaves Infrared Visible light Uv rays Xrays Gamma rays -visible light only part of electromagnetic psectrum that can be detected by human eye .
Why does the electromagnetic psectrum called a continous spectrum ?
-as cut off point ebtween types of waves unclear .
-EM waves do not a medium to travel in can also travel in a vacuum (space)
they all travel at the same speed here
(3*10ti the power of 8 m/s)
-different amterials absrb transmit or reflect EM waves ..
What are radiowaves used for ?
- Used to transmit radio and terrestial tv signals .
- Radiowaves used as theycan travle long sdistances before beign absorbed (by builidngs and trees )
- longer wavlength radio waves spread out beween hills .
- radiowaves can also relflect layer of charged particles in ammosphere which is hwy they can send bery long distances .
What are microwaves used for ?
-sed ofr heating foodds - most foodd contains water
molecules ,
-Watermoelcules absor the enrgy of microwaves .
-enegry causes the temp of the food to increase .
-Also used to communicate with satellites in spaces - as microwaves can pass thorugh Earth without beignrefelected or refracted .
What are iNFRARED WAVES USED FOR ?
- EMMITED BYE ELCTRIAL HETERS , USED TO COOK FOOD IN THE OVEN
- tHAT IS BECAUSE THE ENRGY OF INFRARED OBJECTS ARE ABOSRBED EASILY ABSORBED OBJECTS .
- ALSO USED IN INFRARED CAMERAS TO CHEKCK HEAT LOSS .
What is visible light used for ?
- Used for communicating using fibre opitcals . -Optical firbres (thin strands of galss ) transmit pusles of lihgt down theese fibres and we use thesee puelses to carry information .
- Used to carry telephone and cable Tv signals .
- Shortwavelength carry a great deal of information .
What is UV light used for ?/
- Improtnat use of UV is enegry efficent light bubls .
- Created inside a nbulb , shorwavelength carries more enery than visie light , energy of uV light abosrbed by energy efficent bulb and converted into visible light - requires less energy
- Sun tanning - danger of skin cancner and premature aging of skin .
What are xrays used for ?
Both used for medicial imaging
-Gamam rays detectcancers and treat tjem
-both very penetrative
however xrays can be absorbed by the bones .
