Topic 3: Waves

Topic 3: Waves

1. Waves that need a medium to travel through - mechanical waves (ie. sound, water, seismic waves). An example of waves that don't need a medium is EM waves. There are 2 types of waves; transverse and longitudinal

   • Transverse waves oscillate at right angles in the direction of propagation of the wave.
   • Longitudinal waves disturb/oscillate parallel in the direction of propagation of the wave. These two waves can be demonstrated through a slinky.
   • Waves that travel from one end of the slinky to another are called progressive waves, Waves on ripple tank is known as circular waves, often in sea they appear as a series of parallel line like those on ripple tank - plane waves.Waves with infinit length( no beg,. no end)- continous waves. Waves that have a beg. and end -wave trains. Waves with no repeated motion (a very short wave)- pulse

2. The circle is known as a wavefront, passes every point of the ripple (usually has the same phase)(crest). The lines that pass the wavefronts at 90 degrees are known as rays.

   • wave speed=frequency x wavelength frequency=1/time period

3. Points are whole wavelength apart - in phase, while wavelength/2 apart oscillate in antiphase. A series of compression and rarefractions. 2pi radians- 360. pi/2 radians - 1/4 cycle. 3pi/2 radians -3/4 of the cycle. More info- refer to book notes.

   • Superposition is when two or more waves meet, total displacement at any point= sum of displacements that each individual wave would cause at that point. Path difference between waves involved. Waves can be classified as prpogressive and standing waves, Progressive waves have peaks and troughs, these important as their properties as energy carriers. Stationary waves - standing waves
   • wavelength=2l/n (n= no of nodes/ l=length) wavelength=square root of (tension/mass per unit length) wavespeed=2fl/n frequency=n/21 x square root(tension/mass per unit length)
   • rate at which Amplitude of vibrations increase- attack.. Rate at which amplitude of vibrations decrease - decay;