1. Waves

2. Wave Definition
A wave is an oscillation that travels from one place to another.
Because waves can change motion, we know that waves are a traveling form of energy.
Waves also carry information, such as conversations, pictures, or music.

3. Common Properties
Like oscillations, waves have the properties of frequency, period, and amplitude.

4. Transverse Waves
Oscillations are perpendicular to the direction of the wave moves.

5. Longitudinal Waves
Vibrations in the same direction as the wave moves.

6. Wave Components
Crest: the high point of a wave Trough: low point of a wave

7. Wavelength
Wavelength: the distance from any point of the wave to the same point on the next cycle of the wave.
Denoted by the Greek letter “Lambda” (l)

8. Q1
Waves on a string and water are examples of ____, and oscillate perpendicular to the direction the wave moves.

9. Q2
The low point on a wave is called its:

10. Q3
Sound waves are ____, and oscillate in the same direction as the wave motion.

11. Speed of Waves Different from the speed of a regular moving object.
The speed of a wave is the speed at which the wave’s oscillations travel through a material.

13. Example 1
The wavelength for a wave is 0.5 meter, and its frequency is 40 hertz. What is the speed of this wave? speed = 40 Hz × 0.5 m = 40 (1/s) × 0.5 m speed = 20 m/s The speed of the wave is 20 m/s.

14. Q 1
The frequency of a wave is 50 hertz and the wavelength is meter. What is the wave speed? Answer: 0.05 m/s

15. Q 2
The period of a wave is 10 seconds and the wavelength is 2 meters. What is the wave speed? Answer: 0.2 m/s

16. Q 3
A piano string tuned to middle C vibrates with a frequency of 262 Hz. Assuming the speed of sound in air is 343 m/s, find the wavelength of the sound waves produced by the string m

17. Standing Waves
A wave that is confined to a space.

18. Wavelength in standing waves
Wavelength is one complete “S”

19. Harmonics The lowest natural frequency is called the fundamental.
Harmonics are other natural frequencies.

20. Number of antinodes denotes the number harmonic.

21. Wave Motion
Propagate: waves propagate, meaning they spread out from where they begin.
Plane Waves: for a pattern of parallel straight lines.
Circular Wave: Form a patter of circular wave fronts.

22. Wave Interference
Two different material objects can never occupy the same space at the same time.
Because mechanical waves are not matter but rather are displacements of matter, two waves can occupy the same space at the same time.
The combination of two overlapping waves is called superposition.

23. Superposition Principle
The total vibration at any point is the sum of the vibrations from each individual wave.

24. Wave Interference
In constructive interference, individual displacements on the same side of the equilibrium position are added together to form the resultant wave.

25. Wave Interference
In destructive interference, individual displacements on opposite sides of the equilibrium position are added together to form the resultant wave.

26. Interference

27. Reflection Free boundary Fixed boundary
What happens to the motion of a wave when it reaches a boundary?
At a free boundary, waves are reflected.
At a fixed boundary, waves are reflected and inverted.
Free boundary Fixed boundary

28. Standing Waves
A standing wave is a wave pattern that results when two waves of the same frequency, wavelength, and amplitude travel in opposite directions and interfere.
Standing waves have nodes and antinodes.
A node is a point in a standing wave that maintains zero displacement.
An antinode is a point in a standing wave, halfway between two nodes, at which the largest displacement occurs.

29. Standing Waves

30. Standing Waves
This photograph shows four possible standing waves that can exist on a given string. The diagram shows the progression
of the second standing wave for one-half of a cycle.

31. Reflection The wave bounces and goes in a new direction.
The wavelength and frequency are usually unchanged.
Example: An echo

32. Refraction The wave bends as it crosses a boundary.
A wave is refracted as it passes through the boundary.
Example: eyeglasses

33. Diffraction
The process of bending a wave around corners or passing through openings.
Usually changes the direction and shape of the wave.
Example: Hearing through a tiny crack in the door.

34. Absorption
The amplitude of a wave gets smaller and smaller as it passes through a material.
Wave energy is transferred to the absorbing material.
Example: Heavy curtains, sunglasses

36. http://www.youtube.com/watch?v=hD2hRoB1S Bw