Physical Science - Chapter 17 

Periodic Motion and Waves

17A Periodic Motion

• @@Periodic Motion@@: motion that repeats in equal time intervals

• @@Period@@: the time interval (T) for one complete cycle of the periodic motion

• Periodic Motion of a Spring System

1. Compressing the Spring
2. The Expanding Spring
3. Momentum Stretches the Spring
4. Spring Compresses Again
5. The Recoiling Spring

• Using Periodic Motion
  • @@Damping@@: reducing the amplitude of periodic motion by applying a force that works against the motion
  • @@Damped Oscillator@@: a system that is designed to oscillate but includes a force to reduce the amplitude
  • @@Driven Oscillator@@: a system that is designed to oscillate at a constant amplitude by including a force to overcome frictional losses
  • @@Resonance@@: an increase in the amplitude of a vibration due to additional wave input

17B Waves

• Defining Waves

  • @@Wave@@: a disruption that carries energy from one location to another
  • @@Mechanical Wave@@: a wave that carries energy through a physical medium
  • @@Electromagnet Wave@@: a disruption in an electromagnetic field that carries energy, even through the vacuum of space

• Describing Waves

  • @@Crest@@: the highest point of a wave
  • @@Trough@@: the lowest point of a wave
  • @@Wavelength@@: the distance between two identical points on successive waves
  • @@Wave Height@@: the vertical distance between the trough and crest of a wave
  • @@Amplitude@@: the maximum displacement from the equilibrium position during periodic motion

• Classifying Waves

  • @@Transverse Wave@@: a wave in which the disruptions move perpendicular to the direction of wave travel
  • @@Longitudinal Wave@@: a wave in which the disruptions are parallel to the direction of wave travel
  • @@Compression@@: a region of high density and pressure in a longitudinal (compression) wave
  • @@Rarefaction@@: a region of lower density and pressure in a longitudinal (compression) wave
  • @@Surface Wave@@: a wave that occurs along the interface between two media

• Measuring Waves

  • @@Frequency@@: the number of waves or cycles that occurs per second

17C Wave Behavior

• Behavior of Waves

  • @@Reflection@@: the bouncing of waves off a surface
  • @@Regular Reflection@@: reflection that occurs when a smooth surface reflects light rays in mostly the same direction; also known as specular reflection. A perfectly regular reflection is mirror-like, reflecting all rays and wavelengths uniformly
  • @@Diffuse Reflection@@: the reflection off a rough or uneven surface that reflects light rays in all directions
  • @@Refraction@@: a change in wave direction due to a change in a wave’s speed as it enters a new medium

• @@Standing Wave@@: a wave that is moving even though the locations of the crests and troughs appear to be stationary

• @@Doppler Effect@@: the perceived change in the frequency of a wave due to the motion of the wave’s source or of the receiver