SP4

• what is the equation for frequency?

  frequency = number of oscillations / time
• in terms of period, what is frequency equal to?

  frequency = 1 / period
• what changes when a wave travels from 1 medium to another?

  wave speed and wavelength
• what doesn't change when a wave travels from 1 medium to another?

  frequency
• the speed and wavelength are directly proportional, what does this mean?

  if the speed doubles, the wavelength doubles.

  if the speed halves, the wavelength halves.
• why is the frequency unchanged when a wave passes from 1 medium to another?

  the source is producing the same number of oscillations (vibrations) per second.
• when do reflections happen?

  when a wave hits a flat surface (plane) and bounces off.
• what can often lead to refraction?

  transmission
• what happens when the wave crosses to the new medium?

  the change in the wave's speed will cause the direction of the wave's motion to change and the wave will appear to bend. This is refraction.
• what is the angle of incidence?


  the angle between the incident (incoming) light ray and the normal.
• what is the angle of reflection?

  the angle between the reflected light ray and the normal.
• what is the law of reflection?

  angle of incidence = angle of reflection
• what does it mean if light slows down as it enters a new medium?

  this medium is more "optically dense".
• what happens when light enters a more optically dense material?

  it's refracted closer to the normal.
• what does it mean if the light is refracted closer to the material?

  the angle of refraction is smaller than the angle of incidence.
• what does it mean if light speeds up as it enters a new medium?

  this medium is less "optically dense".
• what happens when light enters a less "optically dense" material?

  it's refracted away from the normal.
• what does it mean if the light is refracted further from the normal?

  the angle of reflection is larger than the angle of incidence.
• in what 3 ways can a wave's motion be changed?

  • reflection
  • refraction
  • diffraction
• what is diffraction?

  when a wave reaches a narrow gap in a surface, they will continue to travel through the gap and spread out in the area beyond the gap.
• what type of waves are seismic waves?

  infrasound waves (below 20Hz).
• Our ears are designed to detect vibrations and transfer the information to our brain via the what?

  auditory nerve
• what happens to sound the more rigid the medium is?

  the higher the speed of the sound wave through the medium.
• what happens to sound the more compressible the medium is?

  the slower the speed of the sound wave through the medium.
• why is the speed of sound in a gas very slow?

  gases are readily compressible (easy to squash).
• why is the speed of sound much higher in solids than liquids and gases?

  solids are significantly more rigid than liquids and gases and are very hard to compress.