Stationary Waves Flashcards
(23 cards)
What is superposition?
When 2 waves meet at the same point in space at the same time
Principle of superposition?
The resultant displacement is the sum of the waves’ individual displacements
What is constructive interference?
When 2 waves are in-phase, the resultant displacement is increase
What is destructive interference?
When 2 waves are in anti-phase and the resultant displacement is decreased
What does it mean if 2 waves are in-phase?
their maximum positive displacements (peaks and troughs) occur at the same time
What does it mean when 2 waves are in anti-phase
the maximum positive displacement of one coincides with the max. negative displacement of the other
What does an interference pattern of light tell us?
Light has wave-like properties and can behave as a wave
When would stable interference occur?
When 2 wave sources are coherent
When does coherent mean?
The 2 waves have a constant phase difference
What is phase difference affected by?
Frequency
In terms of phase and path difference, when does maxima occur?
Path difference must be Nλ and the waves must be in-phase (phase difference is 0) for constructive interference to occur and a maxima to be produced
In terms of phase and path difference, when does minima occur?
Path difference must be an odd number of half wavelengths (λ) whilst the phase difference must be in anti-phase (π or at 180°) for destructive interference to occur so a minima can be produced
What is maxima and minima mean?
Maxima = maximum amplitude and intensity
Minima = minimum amplitude and intensity
What is the path difference and phase difference of the central maxima?
0
Phase difference of the 1st order of minima, 1st order of maxima, 2nd order of minima and the 2nd order of maxima?
2nd maxima = 4π
2nd minina = 3π
1st maxima = 2π
1st minima = π
central maxima = 0
1st minima = π
1st maxima = 2π
2nd minina = 3π
2nd maxima = 4π
Path difference of the 1st order of minima, 1st order of maxima, 2nd order of minima and the 2nd order of maxima?
2nd maxima = 2π
2nd minina = 1½π
1st maxima = π
1st minima = ½π
central maxima = 0
1st minima = ½π
1st maxima = π
2nd minina = 1½π
2nd maxima = 2π
What is significant about the path difference of all minima points
It is never a whole number of π. It is always in between
If a microphone picked up sound with an interference pattern what would you hear?
At points of constructive interference, you would hear sound at a high volume and at points of destructive interference you would hear nothing, or a quieter volume
Equation for the frequency of a light source
F = V/λ
frequency = speed / wavelength
Explain the Young Double Slit Experiment an d why it creates an interference pattern
To travel through the slits as a wave, light splits into two waves that go through each slit. When these waves cross over again on the other side, they ‘interfere’ with each other. Where peaks of the wave meet, they enhance each other, but where a peak and a trough meet, they cancel each other out
Why must a monochromatic light be used for the young double slit experiment?
So there is a single wavelength to ensue the light is coherent - The 2 waves have a constant phase difference/frequencies
What does the Young double split experiment prove?
Light has wave-like properties and can behave as a wave
In a light interference pattern, why does the brightness of the fringes decrease the further out from the centre you go?
Intensity is inversely proportional to the cross-sectional area over 1. if the power of the light source stays constant, the light becomes dimmer the further out you go as its covering a larger area/getting further away.
