Chapter 12 - Waves Flashcards
2nd order maxima- path difference
2 λ
2nd order minima- path difference
1.5 λ
1st order maxima- path difference
λ
1st order minima- path difference
λ/2
central maxima
0
2nd order maxima- phase difference
4π
2nd order minima- phase difference
3π
1st order maxima- phase difference
2π
1st order minima- phase difference
π
define path difference
The difference in distance travelled by each wave
what does superpose mean
when 2 waves overlap
What is the difference between interference and superposition
Superposition is the actual physical phenomena, but the interference is what we actually see. Interference is the pattern or effect that is observes by the superposition of waves.
What happens if 2 waves are in phase when they meet?
This will double their maximum, causing a constructive interference.
What happens if 2 waves are in antiphase when they meet?
They will completely cancel each other out, leaving a destructive interference.
What happens if 2 waves are out of phase when they meet?
There will be a degree of destructive interference, but not total.
How is intensity and amplitude related
Intensity = k * amplitude2 (squared)
What is coherent waves
When 2 waves have the same frequency and they maintain the same phase difference.
What is minima
Destructive interference
What is maxima
Constructive interference
How can you find the phase difference from the path difference
For 2 coherent wave differences, PLD as a fraction of the wavelength gives you the phase difference.
Method to calculate the wavelength by using the path difference
Use a ruler to measure the path fro the centre of the first slit to the 1st order maxima. Do the same for the second slit to the maxima. Calculate the difference. The path difference at the 1st order maxima is 1 wavelength. Repeat for the rest of the maxima and minima. Average out the values for the wavelength.
The Young Double Slit Experiment
It involves shining a light through a colour filter and then through a slit, which then shines it into 2 different slits. There 2 different slits create 2 coherent wave sources, which interfere as they overlap. Where they overlap on a screen, this is called the overlap region, where a pattern of alternating bright and dark ‘fringes’ can be seen.
What is the name of the colour filter used in the Young Double Slit Experiment
A monochromatic filter
it only allows colours that are of a specific frequency
How is a stationary wave created
It is formed when 2 waves (same frequency and hopefully amplitude) travelling in opposite directions superpose.
What is a node
At certain points the 2 waves may be in antiphase, where their displacement cancels out. This point is called a node
What is an antinode
The point at which the waves are at thier maximum amplitude
The distance between 2 adjacent nodes is
half the wavelength
In between 2 adjacent waves, how do the particles behave
all the particles oscillate with each other
What happen to the particles on either side of a node
They are in antiphase to one another.
The resultant force is
Basically the stationary force created.
Energy transfer between a progressive wave and a stationary wave
P. Wave: energy transfer in the direction of the wave
S. Wave: no net energy transfer as the waves are moving in opposite direction
Wavelength between a progressive wave and a stationary wave
P. Wave: minimum distance between 2 adjacent points on a wave that are in phase
S. Wave: The distance from one node to the next times by 2.
Phase difference between a progressive wave and a stationary wave
P. Wave: Phase changes across the complete cycle
S. Wave: All particles of the wave between 2 nodes are in phase and are in antiphase either side of the node.
Amplitude between a progressive wave and a stationary wave
P. Wave: All parts of the wave have the same amplitude
S. Wave: Maximum amplitude occurs at the antinode
Why will go through a filter
The plane of polarisation of the EM waves are parallel to the orientation of the filter, in such a way that no or very little light is absorbed.
Why will light not go through the filter
The plane of polarisation of the EM waves is lined exactly perpendicular to the plane of the filter, meaning that all the light is absorbed.
What is the refractive index
It is a ratio of between the speed of light in a vacuum and the speed of light in a given medium.
Equation used to find the refractive index (n)
n = c/ v
The greater the refractive index…
The more the light will refract.
Refractive index equation according to Snell’s Law
n = (sin i) / (sin r)
Refractive index equation according to Snell’s Law going from one medium into another
n1 (sin theta 1) = n2 (sin theta 2)
What is Total Internal Reflection
A wave phenomenon by which light completely reflects back at a boundary between 2 media, as opposed to transmitting across the boundary and refracting back.
What are the conditions for TIR
A medium within which light is incident has a larger refractive index, n, than a second medium.
The incident ray must be more than the critical angle for TIR to occur.
What is the derivation form of c
Root of t/μ.
What can dictate the frequency of a string being plucked
Length
Mass
Tension
Relationship between the frequency and the tension
Proportional.
If you pluck a string twice as hard, the frequency will increase by a factor of root 2
What can dictate the frequency of a closed/ open air pipe stationary waves
Density
Temperature
Speed of the wave.
By what multiples can closed air pipes work?
Only odd multiples of the fundamental
By what multiples can open air pipes work?
Any multiples of the fundamental
By what multiples can strings work?
Any multiples of the fundamental
