1. Wave Theory Essential Question: What is a wave?

2. Answer Me!!!  Give an example of a wave. Then describe what that wave carries.

3. Waves  A wave is produced by an oscillation (vibration) of the medium (material) surrounding the wave source.  Waves transfer energy. They do NOT transfer mass (or material).

4. Stop and Think…  Take 1 minute to discuss with a neighbor how energy can be transferred through a medium without transferring any matter.

5. Amplitude  Amplitude (A) is the height of the wave from rest position.  The more energy a wave has the larger its amplitude. amplitude

6. Wavelength  Wavelength  is the length of the wave, or the distance between identical points in the wave form. Wavelength ( )

7. Frequency  Frequency (f) is the number of waves that pass a point in one second.  Frequency is measured in Hertz (Hz) or cycles/second.

8. Practice Problem A B C Order the three waves from lowest frequency to highest frequency.

9. Period  The period of a wave is the amount of time needed for that wave to complete one cycle.  Period can be determined by the following:

10. Stop and Think…  What does the amplitude of different waves (i.e: water waves, light waves, sound waves) represent?  What does the frequency of these waves represent?

11. Answer Me!!!!!  What is the significance of amplitude in the following waves: Water Sound Light

12. Pulses and Period Waves  A pulse is a single disturbance that moves from one point to another.  A period wave is a repeating pattern of identical pulses.

13. Transverse Waves  A transverse wave is a wave where the particles vibrate perpendicular to the motion of the wave.  The top of a transverse wave is called the crest the bottom is called the trough. Wave Motion Particle Vibration

14. Longitudinal Waves  A longitudinal wave is a wave where the particles vibrate parallel to the motion of the wave. Sound waves are longitudinal waves. Wave Motion Particle vibration

15. Practice Problem 1  A transverse wave is moving with a velocity v along a rope. In which direction will a knot in the rope move as the wave passes through it?

16. Reflection of Waves  If a wave pulse is incident on (hits) a new medium, some of that wave will be reflected, some will be transmitted into that new medium and some will be absorbed.  The wave will be reflected at the same angle that the wave struck the surface (measured from the normal). Light wave Reflected wave Transmitted wave AIR WATER

17. Practice Problem 2  A physics student notices that 4 waves arrive at the beach every 20 seconds. What is the frequency of these water waves?

18. Practice Problem 4 Determine the Amplitude, wavelength of this wave if each hash mark is 1 centimeter.

19. Phase  Two points are in phase if they are the same height above or below the rest position and moving in the same direction.  Two points are out of phase if they are not in phase.

20. Wave Velocity  The velocity of a wave is a measure of how quickly energy is transferred through the medium.  Wave velocity is directly related to both wavelength and frequency. v = f

21. Practice Problem 6  A periodic transverse wave has an amplitude of 0.20 m and a wavelength of 3.0 m. If the frequency of this wave is 12 Hz, what is its speed?

22. Practice Problem 7  Orange light has a frequency of 5.0 x 10 14 Hz in a vacuum. What is the wavelength of this light?

23. Practice Problem 8  A surfacing whale produces water wave crests having an amplitude of 1.2 m every 0.40 seconds. If the water wave travels at 4.5 m/s, what is the wavelength of the wave?

24. Practice Problem 9  Determine the frequency of a ray of light with a wavelength of 6.21 x 10 -7 m.