Wave Textbook Goodnotes Recap Flashcards
Progressive Wave?
A moving wave carries energy from one place to another without transferring energy to the surroundings
Wave causes?
Something making particles or fields oscillate at a source
Wave energy loss?
Oscillations pass through medium or field carrying energy and losing it as it gets further from a source
Wave behaviours?
Reflection, Refraction, Diffraction
Reflection?
When a wave is bounced back when it hits a boundary
Refraction?
Where a wave changes direction and velocity as it enters a different medium because of the change in refractive index
Diffraction?
The wave spreads out as it passes through a gap or round the obstacle
Displacement?
Has the symbol x and is measured in metres and is how far an object has moved from its undisturbed position
Amplitude?
Measured in metres with the symbol a and is the maximum magnitude of displacement
Wavelength?
Measured in metres and has the symbol λ and is the length of one whole wave oscillation otherwise wave cycle
Period?
Has the symbol T and is measured in seconds and is the time taken for a complete wave cycle
Frequency?
Has the symbol f and is measured in hertz and is the whole number of complete wave cycles or oscillations per second passing a given point from the source
Phase?
The measurement of the position of a certain point along the wave cycle and is measured in degrees or radians
Phase difference?
The amount by which one wave lags behind another wave and is measured in degrees or radians
Frequency and Period?
Inversely proportional relationships in the equation. Frequency = 1 / Period
Wave speed equation?
c = d / t
Wave speed = distance / time
c = f x λ
Wave speed = frequency x wavelength
Speed of light?
3 x 10^8 ms-1
Measuring Speed of Sound?
Microphones picking up waves from a signal generator and time and distance between microphone picking it up is recorded.
Measuring wave speed?
Record depth of ripple tank. Use a dipper to create frequency. Use a strobe light to periodically flash. Increase frequency until the same as light. Measure distance between 2 adjacent peaks.
Transverse Waves?
The direction of energy transfer is perpendicular to displacement of particles
Transverse Waves Movement?
Travel as vibrations through magnetic and electric fields with vibrations perpendicular to the transfer of energy
Transverse wave examples?
EM waves, ripples on water, waves on strings, certain types of earthquake waves (s) waves
Transverse wave graph?
Shown on displacement-time graphs and vibrations upwards from centre line has symbol a+ and downwards has a-
Longitudinal waves?
Have the displacement of particles or field parallel to the direction of energy transfer
Longitudinal waves movement?
Alternating compression and rarefaction of a medium the wave is travelling through
Longitudinal Wave graph?
Usually plotted on a displacement time graph
Longitudinal wave examples?
Earthquake waves called p waves and sound waves
Polarised wave?
A polarised wave is a wave which oscillates in a singular direction
Polarising filter?
A polarising filter can be used to polarise waves so they only travel in one direction otherwise plane
No wave polarising?
This is due to two polarising filters being at exactly 90 degrees to each other
Partial Polarisation?
This is from polarising filters not being at exactly 90 degrees or 180 degrees meaning as waves pass through their intensity is reduced
Polarisation evidence?
Only occurs for transverse waves and provides evidence for the properties of transverse waves
Light polarisation discovery?
1808 by Etienne Malus who discovered light was polarised by reflection and disproved light as longitudinal to explain polarisation
Light transverse discovery?
1817 Thomas Young suggested light could be polarised because it was transverse and consisted of vibrating electric and magnetic fields perpendicular to energy transfer
Partially polarised meaning?
Light reflected off certain surfaces
Light property?
A property of light is most light is polarised and has vibrations possible in all directions
Polarisation of light factor?
The amount of polarisation of light is dependant on its angle of incidence
Partial polarisation reduced?
Polarising filters can be used to remove the rays that can cause glare and keep necessary ones
Glare?
If partially polarised light is reflected off reflectable surfaces the unnecessary light can enter the eye causing reduction in quality of what s being seen
Polarising filter function?
If partially polarised reflected light goes through a polarising filter at a right angle you can block some of reflected light whilst letting light vibrating at filters angle however reducing intensity but reducing glare and unwanted reflections
TV and Radio signals function?
TV signals are polarised by orientation of rods on ariel being lined up with transmitting ariel. The signal strength is determined on ariels positioning or tuning
Superposition?
When 2 or more waves pass through each other
Superposition resultant?
At the instant the waves cross the displacements due to each wave combine and then continue on their way
Principle of superposition?
When 2 or more waves cross the resultant displacements equal the sum of the individual displacements
Interference?
The superposition of two or more waves combing constructively or destructively
Constructive interference?
If wave displacements are in the same direction a bigger displacement occurs and this caused by a trough becoming larger by meeting another trough
Total destructive interference?
This is where equal and opposite displacements meet and cancel each other out completely
In-Phase?
When two points are at the same point in a wave cycle and have the same displacement and velocity
Superposed points?
In phase waves constructively interfering with each other
How is a complete wave cycle shown?
It is shown as a multiple of 2π or 360 degrees
What is phase difference on wave?
How far 2 points are apart on a wave cycle and is measured in degrees, radians, fractions
Exactly in of phase?
0 degrees phase difference or 360 degrees phase difference or Odd number of radian multiples or 180 degrees
Stationary wave?
Also called a standing wave. It is the superposition of two progressive waves with the same frequency, wavelength and amplitude and move in opposite directions
Resonant Frequency?
Frequency at which the original wave and reflected wave combine with an exact phase difference of half or complete wavelengths
Stationary wave property?
Stationary waves are transverse waves, form from 2 waves interfering, only formed at resonant frequency
Nodes?
The point at which amplitude is 0 on a stationary wave and where there is total destructive interference
Anti-nodes?
The point of maximum displacement of a stationary wave and where there is total constructive interference
First Harmonic?
A stationary wave vibrating at the lowest possible resonant frequency and is half a wavelength in size
Methods of producing stationary waves?
Reflecting a microwave beam at a metal plate or achieving resonant frequency on a string
Longitudinal waves method?
Putting powder in a loudspeaker. The sound waves produced create nodes which are undisturbed powder and 2 nodes is half a wavelength. The frequency is the frequency of sound produced by the speaker
Factors affecting resonant frequency investigation?
Mass, Length, Tension of string
Mass per unit length units?
kgm-1
Trends of resonant frequency investigation?
Longer string lower resonant frequency, heavier the string lower resonant frequency, lower tension lower resonant frequency
Diffraction factors?
When a gap is much larger than wavelength diffraction is unnoticeable, when the gap is smaller the wave is reflected, optimal diffraction is a few wavelengths wide
Size of object effecting diffraction?
The wider the obstacle the less diffraction and the greater shadow behind the object where the wave is blocked
Monochromatic light?
Light of a single wavelength and frequency which is a single colour and ideal for producing diffraction patterns
Diffraction pattern quality?
White light makes wavelengths diffract by different amounts meaning lower quality, filters improve quality but not as intense as laser so less defined pattern
Diffraction pattern?
Having light diffract to an amount where central maximum and fringes are created from light travelling through gap similar to its wavelength
Fringe pattern cause?
Due to interference of light wave when it diffracts
Bright fringe?
Due to constructive interference where waves from across width of slits arrive completely in phase at the screen
Dark fringe?
Due to destructive interference and is where waves from across the width of slits arrive completely out of phase at the screen
White light?
A mixture of different colours and components of light having different wavelengths
White light diffraction?
When white lights combination of wavelengths is diffracted by different amounts causing to a spectra of light being produces instead of clear fringes
Intensity?
Power per unit area
High intensity of diffraction patterns?
The brightest part of a diffraction pattern located at the central maximum, high intensity is an increased number of released photons, meaning more photons per unit area hitting the central maximum per second making it brighter than other fringes
Central maximum trends?
Increasing slit width decreases amount of diffraction and narrows central maximum making it more intense, longer wavelength increases diffraction widening central maximum making it have a lower intensity
Two source interference?
When 2 waves from two sources interfere to produce a pattern
Coherent waves?
Waves with the same wavelength and frequency with a fixed phase difference
Clearer diffraction patterns from two source interference?
The two sources must be coherent and monochromatic
Two source interference with coherent light?
Intense beam due to troughs and crests lining up which means constructive interference is experienced
Maxima?
When constructive interference at any points is an equal distance from the two sources in phase
Minima?
Points of destructive interference where any points are an equal distance from two sources out of phase
Constructive interference scenarios?
Where path difference is a whole number of wavelengths, where waves are in phase and reinforce with each other
Constructive Interference happening?
nλ being a whole number
Destructive Interference happening?
(n + 1/2) λ being a whole number
Demonstrating two source interference?
Connect an oscillator to a 2 loudspeaker or 2 ripple tank dippers, the loud or quiet spots or larger and smaller waves are the points of maxima and minima of two source interference
Visual interference patterns?
2 transmitter cones with a microwave transmitter probe and the strength of the signal picked up at different distances shows this effect
Young’s Double Slit Experiment?
A laser is shone through 2 slits the similar size of a monochromatic light to create 2 source interference which creates an observable diffraction pattern on a screen
Safety precautions of Young’s Double Slit?
Never shine the laser towards people, wear safety goggles, avoid being near reflective surfaces, turn off the laser when not needed, have warning signs
Double slit formula?
w = λD / s
Fringe Spacing = Wavelength x distance to screen / slit separation
Small angle approximation?
tan-1(slit separation/path difference) = sin-1(fringe width / distance to the screen)
Accurate double slit results?
Measure multiple fringes and divide by fringe number, have a large distance to the screen, have narrowest slit separation for light used
Tested factors in double slit experiment?
Varying distance or slit separation or wavelength to see the effect on fringe width
Newtons Corpuscles theory?
In 17th century Newton said light was made up of tiny particles, corpuscles, explaining reflection and refraction and identified wave properties of diffraction and interference to produce interference patterns which 100 years later Young provided evidence for
Single source difference to two source interference?
Single source produces sharper interference patterns with brighter, narrower and darker bands
Sharp interference pattern?
A diffraction grating with hundreds of slits per millimetre has a large amounts of reinforced beams which combine and create a sharp diffraction pattern
Normal incidence?
Where the beam is at right angles to the diffraction grating
Single source interference diffraction pattern properties?
All the maxima and minima produced are straight lines and there is a central maximum called the zero order
Zero order?
Where the light travels in the same direction as the incidence angle
Orders?
The lines either side of a central maximum and each order is the pair of lines away from the central maximum
What is the diffraction grating equation?
d x sin θ = n λ
slit separation x angle to normal = order x wavelength
nλ meaning?
The path difference of amount of orders from zero maxima
Factors affecting diffraction grating experiment?
Type of slit used not being a double slit card, spacing of maxima measured with ruler, type of laser varying in wavelength
Diffraction grating independent variable?
Varying of “D” the distance to the screen
Diffraction equation trends?
Small angle approximation allows sinθ and tanθ be equal for angle to normal, wavelength and order have a directly proportional relationship
White light diffraction properties?
Diffraction grating diffracts wavelengths by different amounts causing varying amounts of spread, each order creates a spectrum from red on the outside to violet, zero order stays white
What is absorption spectra?
The dark lines corresponding to different wavelengths of light that have been absorbed
Element absorption spectra?
Every element in stars absorb light of different wavelengths which scientists analyse to see composition of elements in them
Diffraction grating uses?
X-rays, crystallography
Speed of light properties?
Fastest in a vacuum, travels slower in materials interacting with other particles
Optically dense?
Where a material slows down the speed of light when it enters it
Optically dense measurement?
Through using the refractive index and the higher the refractive index the more optically dense the material is and the slow light travels through it
Absolute refractive index?
Has the symbol “n” and is the ratio of speed of light in a vacuum compared to speed of light in a material and is a specific property to the particular material
Cs?
The symbol of speed of light in a material
Air refractive index?
Has the value 1 and has the symbol n air
Refractive index formula?
n = c / cs
Refractive index = speed of light in a vacuum/ speed of light in a material
n = n1/n2
Refractive index = absolute refractive index of material 1 / absolute refractive index of material 2
Relative refractive index?
A ratio between 2 materials and is how the speed in material 1 compares to the speed in material 2 and is a property of the interface between 2 materials and is different for most material pairs
Angle of incidence?
The angle of incoming light makes anti-clockwise from the normal
Angle of refraction?
The angle incoming light makes clockwise to the normal
Snell’s Law equation?
n1 x sinθ1 = n2 x sinθ2
Refractive index of material 1 x angle of incidence of material 1 = refractive index of material 2 x angle of incidence in material 2
Light between boundary movement?
The direction changes because the variation in refractive index causes the speed of the wave to change
Refractive index and incidence relationship?
Towards the normal: n1 < n2 means sinθ1 > sinθ2. Away from the normal: n1 > n2 means sinθ1 < sinθ2
Light refracting away from normal?
The angle of incidence increases because the angle of refraction gets closer to 90 degrees and when critical angle is achieved the light is refracted along the boundary of the material
Critical angle property?
This angle and incidence of refraction along the boundary can happen at a boundary with a different refractive index to where the incidence beam is coming from
Critical angle formula?
n1 = 1 / sinθc
refractive index of material = 1 / critical angle for material to air boundary
Total Internal Reflection?
Refraction doesn’t happen and all the light is reflected back into the material as the angle of incidence is greater than the critical angle
Optical fibre?
A very thin flexible tube of glass or plastic fibre which can carry light signals over long distances using total internal reflection
Step index optical fibre properties?
High refractive index for an optically dense core surrounded by cladding of a lower refractive index to allow total internal reflection to happen
Cladding property?
Protects the fibre’s core from scratches which could cause the light to escape the fibre
Light movement in optical fibre?
Narrow so light shone through hits core and cladding boundary greater than the critical angle so its totally internally reflected repeatedly until it reaches the other end
Optical fibre use?
Used to transmit phone and TV signals instead of using electricity through copper cables
Fibre optic compared to electrical cables?
Optical fibre signals carry more information due to higher frequencies, less energy loss, no electrical interference, cheaper manufacturing, signals can travel further and quicker, minimal signal loss
Signal?
Information sent down optical fibres as pulses of light
Signal degration?
A signal can be degraded by absorption or dispersion causing information to be lost
Absorption?
Where some of the signals energy is absorbed by the material the fibre is made from and the energy loss results in a reduction in signal amplitude
Dispersion types?
Modal dispersion and material dispersion
Pulse broadening?
A consequence of dispersion where the received signal is larger than the initial signal
Broadened pulse consequence?
Pulses overlap each other which leads to information loss
Modal dispersion?
Caused by light rays entering the optical fibre at different angles
Modal dispersion consequences?
Different paths are taken by the light varying from the straight path resulting in different wavelengths arriving at different times
Modal dispersion prevention?
Have an optical fibre with a narrower diameter otherwise a single mode fibre so the light can follow a narrow path
Material dispersion?
Different wavelengths experience different amounts of refraction meaning the wavelengths have different speeds and arrive at different times
Material dispersion prevention?
Monochromatic light, optical fibre repeater
Optical fibre repeater?
Used to regenerate signals every so often so signal degrading is reduced for absorption and dispersion
