WAVES

WAVES

1. Stationary- The superposition of two progressive waves

   • Progressive
     • Transverse- Vibrate at right angles to the direction of energy transfer
       • Polarisation- Only transverse waves are polarised
       • Electromagnetic waves
         • Proof that all EM waves are transverse
         • All waves travel at the same speed in a vacuum
         • Consist of magnetic and electric waves that travel and vibrate at right angles together in phase
         • Emitted by charged particles when they lose energy
       • Reflection
         • Refractive index
           • Density- mass per unit volume
         • Total internal reflection
           • Optical fibres
           • Different wavelengths move at different speeds through dense substances
         • Colours split due to different colours of white light having different wavelengths
           • Rainbows
     • Longitudinal-Vibrate along direction of energy transfer
     • Superposition- when two or more waves cross
       • Interference- can be destructive or constructive
         • Single/double slit
           • Light intensity
             • Photons - packets of electromagnetic radiation
           • Diffraction
             • Diffraction of white light creates a spectrum
           • Diffraction gratings
             • Light spectra
         • Coherent sources - same wavelength, frequency and constant phase difference
         • Phase difference - in step
           • When waves are in phase we get constructive interference
           • When waves are out of phase we get destructive interference
   • No energy transmitted
   • Oscillating loops-seperated by nodes
     • First harmonic-one loop with nodes at each end
     • Secondary harmonic-two loops, node in the middle and one at each end
     • Third harmonic-three times the frequency to the first harmonic

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