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Waves & Optics - Coggle Diagram

- - - - direction of oscillations is perpendicular to direction of energy transfer/wave propagation
      - e.g. EM waves, secondary seismic waves (S waves)
    - - direction of oscillations is parallel to/in same direction as energy transfer/wave propagation
      - e.g. sound waves, primary seismic waves (P waves)
- - - - the fraction of a cycle between two particles (oscillating at the same frequency)
- - - - 2 peaks/crests (supercrest) OR 2 troughs (supertroughs)
      - occurs at antinodes
    - - peak & trough (positive and negative displacement combine and cancel out)
      - occurs at nodes (0 displacement)
  - - - same f & λ (and hence v)
        
        same amplitude
        
        moving in opposite direction
  - - - frequencies at which a stationary wave is formed
    - - Earthquakes
        
        pendulums, mass dampers, rubber shock absorbers & steel lattice frames used to reduce effects of seismic waves
  - - - lowest frequency at which a stationary wave can be formed (1/2 λ)
      - 2 nodes; 1 antinode
    - - frequency is double 1st harmonic; wavelength is half (for constant length of string)
        (x2 frequency = ÷2 wavelength - constant speed)
- - - - Coherent - same freqeuncy & constant phase difference
      - Monochromatic - single wavelength (frequency or photon energy)
      - Safety
        
        never shine at eyes
        
        wear protective eyewear
        
        avoid reflective surfaces
        
        display laser warning signs
      - clear diffraction/interference pattern
    - - central white fringe; alternating bright fringes; spectra (violet closest to centre/red furthest from centre); wider maxima
    - - waves arrive at screen in phase
      - path difference = nλ
      - constructuve interference
      - maximum formed
    - - waves arrive at screen in antiphase/exactly out of phase
      - path difference = (n+1/2) λ
      - destructive interference
      - minimum formed
    - - w = λD/s
- - - - bright central fringe = 2x width & more intense than subsidiary maxima
      - alternating dark & bright fringes = same width
    - - increase slit width = less diffraction = central max narrower & more intense
      - increase λ = more diffraction = central max wider & less intense
      - W = 2λD/a
  - - - dsinθ=nλ
      - d = 1/D
      - increase λ or decrease d = increase angle of diffraction
    - - shar, bright/intense
      - diffracted waves reinforce one anther in certain directions & cancel out in others
      - central parallel beam; n = 0 order
    - - chemical analysis
      - analysis of light from stars
      - X ray crystallography
- - - - angle of incidence exceeds critical angle
      - n1 > n2
    - - where all light is refracted along boundary/perpendicular to normal
      - sinθc = n2/n1
    - - thin, flexible glass/plastic fibres carrying information as light signals
      - more optically dense core is transmission media for light signals/pulses/propagation
      - surrounded by less optically dense cladding to protect core from damage and prevents signal degradation/crossover of pulses; allows TIR to occur
      - Advantages (compared to copper)
        
        light pulses/signals carry more information (light has higher frequency)
        
        light doens't heat up fibre (no resistance/almost no energy absorbed/escapes)
        
        no electrical interference = more secure
        
        cheaper to produce
        
        signal can travel long distances very quickly (minimal signal loss)
      - Signal Degradation
        
        Absorption
        
        part of signal absorbed by fibre, reducing amplitude (not such a problem as signals are digital)
        
        Dispersion
        
        Multipath/Modal - light rays enter fibre core at different angles; take different paths; arrives at end at different times (takes different amount of time)
        
        pulse broadening - reduced by narrower cores, monomode fibres & using monochromatic light (USE SIGNAL REPEATERS/AMPLIFIERS)
        
        Material - light consisting of different λ refract different amounts & travel at different speeds
  - - - vacuum = 1.00
      - air = 1.000277 ≈ 1.00 (3sf)
      - water = 1.33
      - ice = 1.31
      - glass = 1.40 - 1.50
      - diamond = 2.417