1. Chapter 15

2.  Every sound, light and water wave that is heard and seen depends on waves  A wave is a disturbance that transfers energy from one place to another  A wave can transfer energy over a distance w/o moving the matter the entire distance  Forces can send a wave through material

3.  A medium is any substance that a wave moves through  This would include all gases, liquids and solids

4.  There are 3 types of waves 1. Mechanical- wave that transfers energy through matter 2. Transverse- the direction in which the wave travels is perpendicular, or at right angles 3. Longitudinal- the wave direction travels the same as the direction of the disturbance

5.  A wave has many properties that help identify and measure it  A crest is the highest point, or peak of a wave  A trough is the lowest point or valley of a wave  Amplitude is the distance b/w a line through the middle of a wave crest or trough  The distance from one wave crest to the very next crest is called the wavelength  The number of waves passing a fixed point in a certain amount of time is called the frequency

6.  A wave’s speed can be measured by finding how long it takes for a wave to get from one point to another  The formula used to calculate a wave’s speed is:  Speed= wavelength x frequency

7.  Waves bounce  The bouncing back of a wave after it strikes a barrier is called reflection  Sometimes waves don’t bounce back when it’s in a new medium  When a wave enters a new medium at an angle it bends or refracts  Refraction is the bending of a wave as it enters a new medium at an angle other than 90 degrees

8.  Diffraction is the spreading out of waves through an opening or around the edge of an obstacle  Diffraction also occurs as waves pass the edge of an obstacle

9.  Two waves can add energy to take away energy from each other in the place where they meet  Interference is the meeting and combining of waves  The adding of two waves is called constructive interference b/c it builds up or constructs a larger wave out of two smaller ones  Destructive interference usually happens when identical waves meet but are not usually aligned  Some crests meet up with crests in some places and troughs in other places