# Topic 4 Wave - Overview!

?
• 8. Nature of waves
• 8.1 Mechanical Oscillation
• Requires a medium!
• Longitudinal waves
• Particle oscillate parallel to wave motion
• e.g. Sound
• Compression
• Rarefactions
• Mechanical waves
• Particle oscillate perpendicular to wave motion
• displacement-distance graph and Displacement-time graph
• Phases
• Out of phase
• Antiphase
• Phase difference of 180°
• Phase difference
• Wave form
• Wave profile
• Sinusoidal
• Distance between two Adjacent positions that are in phase is the wavelength of the wave
• 8.2 Electro-magnetic waves
• Created From accelerating Charged particles
• Also created from Quantum jumps by an electron in an atom or excited nuclei
• Electro-magnetic waves produced by the latter are Photons
• Requires no Medium!
• A varying Electric field cannot exist without a magnetic field
• 8.3 Wave Equations
• V=?/T
• f=1/T
• Wave Equation
• V=?f
• When a wave is incident on an interface between two different media the energy may be absorbed, transmitted or reflected
• x=vt/2
• Calculating distance using sound
• Example of constructive & destructive
• Two in phase waves producing maximum amplitude (A+A=2A)
• Two anti-phase wave producing zero amplitude
• Destructive superposition
• Example of constructive & destructive
• Two in phase waves producing maximum amplitude (A+A=2A)
• S2P1-S1P1=n?
• n=the order of the maximum from centre (e.g 1st or 2nd maximum)
• Basic
• Constructive superposition
• Destructive superposition
• 10. Superposition of wave
• 10.2 standing waves
• Produced by superposition of two progressive waves of equal frequency and amplitude moving in opposite directions
• nodes
• Zero amplitude
• Antinodes
• Max amplitude
• Diff. between progressive waves (PW) and standing waves (SW)
• SW store energy, PW transfer energy from point to point
• Amplitude of SW vary from 0 to Max, PW have constant amplitude
• SW oscillations are in all in phase between nodes, PW phases vary continuously
• Standing waves on string
• Melde's exp.
• Sonometer
• harmonics
• Overtones
• Fundamental frequency
• Standing wave with 2 nodes and 1 antinodes
• String instruments
• Differentiate between instruments, by quality/timber of notes
• Difference is that wind can be either a node or antinode at wave boundaries
• Standing waves on wind instr.
• ???
• Electron Diffraction
• ?= h/mv
• h= planck's constant= 6.6x10-34
• Standing waves on wind instr.
• ???
• Close end(s) = node
• Open end(s) = antinodes