P1.5

P1.5

1. the nature of waves

   • we use waves to transfer energy and information
   • mechanical waves:
     • water waves
     • sound waves
   • electromagnetic waves
     • light waves
     • radio waves
     • microwaves
   • transverse waves
     • the vibrations are perpendicular to the direction in which the waves transfer energy
   • longitudinal waves
     • the vibrations of a longitudinal wave are parellel to the direction in which the waves are travelling

2. measuring waves

   • amplitude
     • the hight of the wave crest or depth of the trough
   • wavelenght
     • distance from one wave crest to another
   • frequency
     • the number of wave crests passing one point in a second
   • wave speed (v)= frequency x wavelength

3. reflection

   • the normal is perpendicular to the mirror
   • angle of incidence= angle between incident ray and the normal
   • angle of reflection= angle between the reflected ray and the normal
   • angle of incidence= angle of reflection

4. refraction

   • the change of direction of waves when the travel across a boundary
   • when entering a glass block, the ray will turn slightly to the normal
     • and when it exits it turns back away from the normal

5. diffraction

   • the spreading out of waves when they pass through a gap or round the edge of an obstacle
   • the narrower the gap the greater the diffraction
   • if radio waves do not refract enough the signal will be poor

6. sound

   • sounds waves are vibrations that cannot travel through a vacuum
   • echoes are due to sound waves reflected off a smooth hard surface

7. musical sounds

   • the pitch of a note increases if the frequency increases
   • the loudness of a note increases if the amplitude increases
   • vibrations when instruments are played produce sound waves