topic 4 - waves

• frequency

  the number of waves that pass a point per second. it is measured in hertz

  1Hz - 1 wave per second
• amplitude

  the distance from the top to the mid point of wave
• period

  the time it takes one complete wave to go past
• wavelength 


  the distance between two successive crests or troughs
• rest position

  the undisturbed position of particles of fields when they are not vibrating
• displacement

  the distance of a certain point in the medium that has moved from its rest position
• peak / crest

  the highest point above the rest position
• trough

  the lowest point below the peak / crest
• velocity

  the speed of wave expressed in metres per second
• wave

  a wave is a disturbance or oscillation that travels through space, transferring energy
• longitudinal waves


  a type of wave thats oscillations are parallel to the direction of the waves. it needs a medium to travel through

  example : soundwaves

  
• transverse waves


  a type of wave in which the oscillations occur at right angles to the direction of the waves. they don’t require a medium to travel through

  example : electromagnet / light waves

  
• formula for wave speed

  wave speed = distance / time

  ( m / s ) ( m ) ( t )

  ( s = d / t )
• incident ray

  the path of the incoming light before it strikes a reflecting surface
• reflected ray

  the path of light after it bounces off a reflecting surface
• normal

  an imaginary line perpendicular to the surface at the point of incidence
• angle of incidence

  the angle formed between the incident ray and the normal
• angle of reflection

  the angle formed by between the reflected ray and the normal
• infrasound

  sounds with s frequency lower than 20Hz. it’s too low to be heard by humans. earthquakes and volcanoes produce infrasounds called seismic waves
• ultrasound

  sounds with a frequency higher than 20,000Hz. it is too high to be heard by humans. many animals including bats and dolphins use ultrasound to communicate and find prey
• how we hear

  the eardrum vibrates due to sound waves making it vibrate. vibrations are passed down to the tiny bones to amplify the vibrations passed to the cochlea. tiny hairs in the cochlea detect these vibrations creating signals called impulses . impulses travel along the neurones in the auditory nerve to reach the brain
• sonar system ( sound navigation and ranging )

  a technology that uses sound waves to detect snd locate objects underwater. a sonar system emits sound pulses, typically at ultrasonic frequencies into water
• compression

  where the medium is squashed together
• rarefaction

  where the medium is stretched apart