Waves Flashcards
Plane-polarised light
Light with waves constituting vibrations in only one plane.
Malus’ law [Equation]
I=Imax * cos^2(theta)
Coherence
Two waves are coherent if they have {the same frequency an wavelength, and} a constant phase difference between them.
Phasor
Spinning vector that represents the phase of a wave
Path difference
Difference in the distance travelled by two coherent waves (that are in phase?) to get to a given point.
Phase/path dif. [eq]
Phase diff = (2 * pi * path diff)/ lambda
Principle of Superposition
When two or more waves cross, the resultant displacement equals the VECTOR sum of the displacement of each wave.
Standing wave
A wave formed by the superposition of two progressive waves with the same wavelengths, travelling in opposite directions, at a resonant frequency.
No energy transmitted
Nodes and antinodes
Standing wave vs progressive wave
- No energy transmitted vs energy transmitted.
- A pattern of nodes (zero displacement) and antinodes (max displacement), i.e. the amplitude of the wave is different at different points along the wave. VS progressive wave: at any point in space along the wave, the medium of the wave vibrates with the same amplitude.
https: //physics.stackexchange.com/questions/248460/progressive-and-stationary-waves-amplitudes-confusion
Diffraction
The spreading out of waves as they pass through an aperture or go around an obstacle.
Optical fibre functioning
Carry signals in the form of light pulses over long distance, using the phenomenon of TIR.
- Refractive index of core material is greater than that of the cladding material. n1>n2
- The light enters the tube such that the angle of incidence when the light hits the wall is greater than the critical angle. i>c.
sini/sinr = n2/n1, so if n2c, then totally internally reflected.
Phase difference
The fraction of an oscillation by which one wave leads or ‘lags behind’ another.
Young’s double slit formula
We know nλ = dsinθ for maxima. (Now let’s call d “a” …)
For n =1: λ = asinθ.
Also, if D is distance from slits to screen, then tanθ = x/D where x is fringe separation.
Small angle and D»a:
λ/a = x/D ⇒ λ = ax/D