chapter 9-11 waves

• waves are caused by a disturbance or vibrations. they transfer energy but not matter (refers to the medium, medium only vibrates about a fixed position and does not travel with energy). speed of a wave is independent of its frequency and amplitude. waves can be reflected or refracted.
• longitudinal waves

  direction of wave motion is parallel to the direction of vibration
• transverse wave

  direction of wave is perpendicular to the direction of vibration
• longitudinal wave

  compressions are regions where particles are closely packed together
• longitudinal waves

  rarefactions are regions where particles are further apart
• wavefronts are imaginary lines joining all points that are of the same phase.
• the speed of sound in air is 330m/s. speed of light in a vacuum is 3.0x10^8 m/s.
• sound waves are longitudinal waves as the wave is vibrating parallel to the direction of energy transfer
• sound waves need a medium to travel in as they are carried from one place to another by molecules of matter. air molecules do not move but instead vibrate about their fixed positions. they then come together in areas called compressions and extend away from each other in areas called rarefactions.
• sound travels fastest in solids as solid molecules are packed closest together allowing sound to travel at higher speeds
• loudness affects the amplitude of the sound waves produced. louder sounds will result in higher amplitude and vice versa.
• speed of sound increases in humid weather as there are more water molecules to transfer energy from one molecule to another.
• speed of sound increases in warm weather as air particles have more energy in their kinetic store and are able to collide with each other more readily.
• as frequency increases, pitch also increases and vice versa
• electromagnetic waves can transmit energy without transferring matter. this allows EM waves to be transmitted through a vacuum without involving any material medium.
• radio waves - comms, MRI scans to provide imagery of nerves, blood vessels and soft tissues
• microwaves - satellite comms, radar for aircraft navigations, ovens.
• infrared waves - tv remote controls, thermal imaging

  visible light - photosynthesis, human vision

  uv waves - sterilisation, phototherapy

  x rays - medical diagnosis, airport security banners

  gamma rays - cancer treatment, nuclear industries
• the higher the frequency of EM waves, the more energy it carries.
• wavelength is measured from one peak to another peak or trough to trough.
• frequency = speed / wavelength
• electromagnetic spectrum

  • radiowaves
  • microwaves
  • infra-red
  • visible light
  • ultraviolet rays
  • x-rays
  • gamma rays