Wave

• Wave is a disturbance that travels through a medium or a vacuum and carries energy
• Wave train or periodic wave - a succession of periodic disturbances
• Examples of waves in everyday life:

  • Light waves enable us to see
  • Sound waves allow us to hear
  • Radio waves transmit information
  • Microwaves are used in cell phone communication
  • Microwaves are used in microwave ovens for cooking
  • Ultrasound and X-rays are used in medical diagnosis
  • Ultraviolet rays are used to sterilize medical devices
  • A Slinky toy can be used to observe waves
• Characteristics of waves:

  • Frequency: number of waves produced per unit time, measured in hertz (Hz)
  • Period: time for one complete cycle of a wave to pass a reference point, reciprocal of frequency. as a measure of time, is expressed in units of time, usually seconds.
  • Wavelength: distance between two successive points in phase with each other in a wave
  • Speed: distance traveled by a wave per unit time
  • Amplitude: maximum displacement of a particle on a medium from its resting position
• Transverse waves:

  • Particles vibrate perpendicular to the direction of wave propagation
  • Consist of alternating hills and valleys
• Longitudinal waves:

  • Particles vibrate parallel to the direction of wave propagation
  • Wavelength is the distance between consecutive rarefactions or compressions
• Body waves:

  • Travel through Earth's interior
  • Divided into Primary waves (P waves) - longitudinal Secondary waves (S waves) - tranverse
• Surface waves:

  • Travel on the surface of Earth
  • Love waves move the ground from side to side
  • Rayleigh waves move the ground up and down
• Energy transmission by waves:

  • Waves transfer energy without significant particle movement
  • Energy is proportional to the square of amplitude
  • Energy is proportional to the square of frequency for mechanical waves
  • Energy of an electromagnetic wave depends on frequency and is inversely proportional to wavelength
• Intensity of a wave:

  • Defined as energy transported per unit area and time
  • Inversely proportional to the square of the distance from the source (inverse square law)
• Energy Transmission by Waves:

  Several factors affect the energy of a wave. Some of these factors are amplitude, frequency, wavelength, and distance.
• Wave Pulse - single unrepeated disturbance
• Mechanical Waves

  • requires a medium to propagate. Example of a mechanical wave is a sound wave. It cannot travel in a vacuum.
• Electromagnetic Waves

  • Can travel in a vacuum and any medium.

  • Examples are radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays
• Transverse Wave

  • the particles of the medium vibrate perpendicular to the direction of wave propagation and consist of alternating hills and valleys
• Longitudinal Wave

  • particles of the medium vibrate parallel to the direction of the wave propagation. In longitudinal waves, wavelength is the distance between any two consecutive rarefactions or any two consecutive compressions.