2.  In chapter 13 we went over:  Work › How work relates to force and distance Transfer and conservation of energy › Power  Now we will learn: › How forces create waves › How waves transfer energy › How waves are classified

3.  Wave: › The disturbance that transfers energy from one place to another  Can transfer energy over distance without moving matter the entire distance. › Ocean waves travel kilometers without the water itself moving the same distance-the water simply moves up and down (disturbance) transferring its energy

4.  Forces start a disturbance which sends a wave through the material:  Rope waves: › If I flick the rope by applying a force upward then quickly apply the opposite force down, it sends a wave through the rope. › Both forces are required to start a wave

5.  Water waves: › When an object is dropped into the water, the force applied causes waves to move through the water › D:\wave-interference_en.jar D:\wave-interference_en.jar  Earthquake waves: › Sudden release of energy that has built up in the rock from a pushing and pulling (force) causes energy waves to be transferred through the ground

6.  Medium: › Any substance that a wave moves through  Water is the medium for ocean waves  Rope is the medium for a rope wave  Mechanical waves: › Waves that transfer energy through matter  What is matter?

7.  Think about an earthquake: › What type of energy is transferred during an earthquake (kinetic, potential, or mechanical) › The disturbance causes the ground to shake from side to side and up and down › As the energy is released, it travels in a wave but the ground itself does not travel with the wave › Faults and Earthquakes Faults and Earthquakes

8.  Transverse waves: › The direction in which the wave travels is perpendicular, or at right angles, to the direction of the disturbance › “transverse” means across or crosswise › Look at the rope wave:

9.  http://vimeo.com/6339850 http://vimeo.com/6339850

10.  Longitudinal waves: › A wave that travels in the same direction as the disturbance  Examples are: › Sound waves  Molecules of air are set in motion which vibrate quickly causing more air molecules to vibrate › Slinky wave demo:  If I pull the slinky back straight and release it, the coils move forward and backward.

11.  When tracking and recording the height of waves in the ocean, scientists use:  Mean: › The average of the recorded heights  Median: › The middle value when all values are recorded from least to greatest  Mode: › The value that occurs the most out of the data set

12.  Measuring wave properties: › Crest:  The highest point or peak of a wave › Trough:  The lowest point or valley of a wave

13.  Amplitude: › The distance between the middle of the crest to the middle of the trough in a transverse wave. › Indicates how much energy the wave is carrying (bigger the wave, the more energy)  Wavelength: › The distance from the crest of one wave to the crest of the next wave › Can also be measured from trough to trough

14.  Frequency: › The number of waves passing a fixed point in a certain amount of time › “frequent” means often  Frequency and wavelength are related: › If the frequency increases, the wavelength shortens › If frequency decreases, the wavelength increases

15.  http://www.classzone.com/books/ml_sci ence_share/vis_sim/wslm05_pg18_graph /wslm05_pg18_graph.html http://www.classzone.com/books/ml_sci ence_share/vis_sim/wslm05_pg18_graph /wslm05_pg18_graph.html

16.  Speed = wavelength times frequency  S=λf  S means speed  λ (Lamda) means wavelength  f means frequency

17.  Reflection: › The bouncing back of a wave after it strikes a barrier  Refraction: › The bending of a wave as it enters a new medium at an angle other than 90 degrees  Diffraction: › The spreading out of waves through an opening or around the edge of an obstacle

18.  reflection and refraction reflection and refraction

20. › D:\wave-interference_en.jar D:\wave-interference_en.jar

21.  Interference: › The meeting and combining of waves › They can add to or take away energy from each other  Constructive interference: › The adding of two waves › Makes a larger wave out of two smaller waves › When joined perfectly, the new amplitude equals the combined amplitudes of the two original waves  Waves can cancel each other out

22. Constructive interference Destructive interference

23.  wave interference wave interference