ch25_hhma


 * //Chapter 25: Vibrations and Waves//**

A wave always has a Sine curve. the top of a way is called **crests** and a low point is called **troughs**. The distance between either the crests or troughs is called the **wavelength**.
 * 25.1 + 25.2**
 * Vibrations** are wiggles in time. **Waves** are vibrations, but they are also a wiggle in space along with time. The time of one swing of a pendulum are called the **period.** A period depends on the length and the gravitational force; (the longer the pendulum, the slower the period.)
 * Simple Harmonic Motion**- the back and forth motion of a pendulum.
 * Frequency** is how often the vibrations occur. Its measured in **Hertz** (Hz). 1 Hertz = 1 cycle per second. Frequency = 1/Period and vice versa.

Wavespeed depends on what it moves through.
 * 25.3 - 25.6[[image:wave_m9.jpg align="right"]]**
 * Wavespeed = frequency X wavelength.**
 * Transverse** **Waves**- When the motion of the medium is at right angles to the direction in whice the wave travels.
 * Longitudinal** **Waves**- Particles move along the direction of the wave.

If you take a rope and hold one end stationary and shake it up and down, it creates the incedent and reflecting waves form a **standing wave.** On a standing wave, the stationary parts are called **Nodes** and the parts with the largest amplitudes are **Antinodes**.
 * 25.7- 25.8**
 * Interference Patterns-** when two waves overlap with eachother, they will either increase, decrease, or neutralize the waves.
 * Constructive interference**- when one crest of a wave of another wave overlaps the crest of another, the effects add together.
 * Destructive** **Interference**- When one crest of a wave overlaps a trough of another wave and the effects cancel out.
 * ||> [] (waves) ||





[] (Standing wave)


 * 25.9 - 25.11**


 * Doppler Effect**- The change in frequency due to the motion of the source. The greater the speed, the greater the doppler effect will be.
 * Blue Shift**- An increase in frequency. Its called that due to the increase towards high-frequencys or the blue end of the spectrum.
 * Red Shift**- A decrease in frequency. Its called that due to the decrease towards low-frequencys or the red end of the spectrum. [] (Doppler effect)

Unlike a speedboat, which creates 2-D bow waves, a aircraft will create a **Shock Wave,** or a 3-D bow wave. When the shell of compressed air from a high-speed plane reaches the listeners below, a sharp crack or **Sonic Boom** will be heard. [] (Bow wave) [] (Sonic boom)
 * Bow Waves**- the crests that appear V-shaped due to the crests overlapping at the edges.

Mike Adams