Waves

Waves

1. Examples:

   • ∙We call the material through which a wave propagates the medium. So far we have seen examples of two mediums: rope and spring steel.
   • ∙Both the rope and the spring were examples of traveling waves, and both traveled in the +x-direction.
   • ∙The rope transferred its wave pulses by vibrations which were perpendicular to the direction of the wave velocity.
   • ∙Any wave produced by vibrations perpendicular to the wave direction is called a transverse wave.

2. Transverse and longitudinal waves

   • ∙The spring transferred its wave pulses by vibrations which were parallel to the direction of the wave velocity.
   • ∙Any wave produced by vibrations parallel to the wave direction is called a longitudinal wave.
   • Transverse waves are perpendicular to the wave velocity.

3. The nature of sound waves

   • Consider a speaker cone which is vibrating due to electrical input in the form of music.
   • As the cone pushes outward, it squishes the air molecules together in a process called compression
     • As the cone retracts, it separates the air molecules in a process called rarefaction.
       • Since the vibrations are parallel to the wave velocity, sound is a longitudinal wave
   • Always in sound waves: there is a pulse velocity v,there is a compression or condensation,there is a decompression or rarefaction, the particles are displaced parallel to v.

4. Wavefronts and rays

   • Rays and wavefronts are perpendicular to each other

5. Crests and troughs

   • Every wave have a crest that is the tallest place in the wave an a trought that is in the lowest plance of the wave in a tranverse wave

6. Rarefaction and compression

   • This exist in logitudinal waves

7. Displacement and amplitude

   • he signed distance from the equilibrium position is called the displacement.
   • The amplitude is the maximum displacement. The amplitude is just the distance from crest to the equilibrium position.

8. Period and wavelength

   • The wavelength λ is the distance from crest to crest (or trough to trough).
   • The period T is the time it takes a wave crest to travel exactly one wavelength.
     • The period is the same for all particles of the medium.

9. Wave speed an frequency

   • The speed at which a crest is moving is called the wave speed
   • The frequency measures how mane wave crests per second pass a given point and is measured in cycles per second or Hz
     • Speed: v= λ /T
     • Frequency: f=1/T