Flashcards
Waves External Notes
Cards in this deck (34)
- 1What is a Standing Wave?Standing waves aka "stationary waves" are produced when two waves of same Amplitude and frequency are travelling in opposite directions.
Places of greatest Amplitude of oscillation = anitodes
Zero Amplitude oscillation & completely destructive interference = nodes - 2Standing Wave Properties:1. Formed when two waves of same frequency travel through each other in opposite directions
2. Same f and y of the waves that made it
3. No energy is transferred
4. Amplitude is the sum of travelling wave amplitudes
5. Antinode = max displacement
6. Node = minimum displacement - 3Instruments info:Instruments produce sound by the vibrations of standing waves in stretched strings or columns of air.
Certain frequencies cause string or air column to resonate, producing a musical note.
Standing wave is produced by a combination of fundament f and harmonics. - 4Changing v in strings- different medium (heavier/lighter)
- different tension
Note: lower v = lower f = lower pitch
(if y is constant) - 5Factors affecting f of string- Length
- Tension
- Heaviness
Note: shorter string = shorter y = greater v
greater tension = greater v - 6PitchIs determined by the length of the air in the column in the tube.
- Shorter column = higher f = higher pitch
Note: can be demonstrated by opening holes in wind blown instruments - 7Open PipeAir is free to undergo its back & forth longitudal motion at the open end of the air columns.
Same formula as string - 8Closed pipeReflected waves from one end of the medium overlap with incident waves from the source.
At the closed end of an air column, air is not free to undergo movement and forms nodes.
Nodes = 0 disturbance = destructive interference at points out of phase
Antinodes = at open ends = constructive interfernce at points in phase - 9Closed pipe harmonicsClosed pipe = no even number of harmonics
Wavelength (y) only fits if there is antinode at open end and node at closed end. Doesn't occur with even number of harmonics.
The tube can only sustain odd harmonics because the tube fits only an odd number of quarter wavelengths.
(E explanation) - 10TimbreSame note on different instruments that sound different.
Bc of multiple harmonics resonating at the same time. And Amplitude & intensity of each harmonic is different.
= unique sound - 11Beats- Beating = regular pulsing of the loudness of the sounds which is heard when 2 sound sources produce sounds of slightly different frequencies. (0-10 Hz)
- 12Beat Frequency Formula:fB = f1 - f2
- 13Diffractionchange in direction of waves as they pass through a gap.
(bending of waves)
Out of phase = quiet
In phase = loud
Diffraction = proportional to y
= inversely proportional to gap size
(y ^ = diffraction^) - 14Constructive InterferencePath difference is multiples of whole wavelengths.
Pd = ny
= Maxima - 15Maxima= Antinodes = bright lines
produced by interference of light waves - 16Destructive InterferencePath difference is multiples of half wavelengths.
Pd = (n/2)y - 17Minima= Nodes = dark lines
produced by interference of light waves - 18Constructive Interference Formula:dsintheta=ny
- 19Destructive Interference Formula:dsintheta=(n-1/2)y
- 20DistanceDecreasing distance between slits = increase distance between fringes & increases angle = fewer spectral lines
(m/e explanation) - 21WavelengthIncreasing y = increase distance between fringes, as long as the slits are wide enough to permit the passage of light of that wavelength.
- 22Small angle approximation formula:ny = dx/L
- 23Diffraction Grating Factors:- Brighter fringes is bc more slits = more light
- Sharper fringes = more waves interacting
- Fringes spread further apart - 24Diffraction Grating Formula for distance:d = 1 / N
- 25Diffraction Grating of white light info:aka dispersion = spreading of white light, where each colour = diff y & f = bend/refract at diff angles
ROYBBIV - (violet on inside, red on outside & central maxima = white, n = 0)
- Red = longest y & lowest f = most diffraction & least refraction
- Violet = shortest y & highest f = least diffraction & most refraction - 26Diffraction through Square Slits info:When white light waves are diffracted by a square shaped gap they are bent by all four edges. So light is diffracted horizontally & vertically so, horizontal and vertical 'spots' on screen.
Antinodal lines (constructive interference) & Nodal lines (destructive interference) occur both horizontally and vertically. - 27Apparent Wavelength:stretched/compressed wavelengths = Apparent Wavelength
- what the observer hears - 28Apparent Wavelength in relation to an observerCompressed (smaller) y = towards observer = higher apparent f = higher pitch
Once it reaches observer, they'll hear the true f
Stretched (longer) y = away from observer = lower apparent f = lower pitch - 29Apparent Wavelength Perpendicular to source info:Unless the person is travelling parallel to source, they will hear a higher f initially as source approaches, then a lower f as source moves away.
- 30Sound Barriercreated by objects that approach the speed of sound, where pressure builds up in front of object.
- Subsonic = constant v , lower than v of sound
- v of sound = v object
- Supersonic = v object is higher than v of sound, a "sonic boom" is emitted. Producing shockwaves. - 31The Doppler Effect= change in f of wave by the moving source
- 32The Doppler Effect 3 formulas:Vw = fy = f'y'
f' = f (vw / vw+-vs)
Source & wave same direction = -
Source & wave different direction = +
f = 1 / T - 33Sources moving in circles- Max v away and towards observer, where y' > y & f' > f
- Travelling perpendicularly (aka sideways) where y' = y & f' = f
(equal) - 34Doppler Shifted Spectra info:- Red = longer y = stretched y = lower f
- Blue = shorter y = compressed y = higher f
Information
- Description
- NCEA Level 3 physics level 3 (Waves External) Flashcards on Waves External Notes, created by Humayra Azam on 10/11/2021.
- Created by
- Humayra Azam
- Views
- 1
- Rating