1. Chapter 8.1 Notes
Waves

2. Wave motion is a transfer of energy, without the transfer of matter.
A single disturbance in a wave is called a wave pulse.

3. Horn Bubble Demo

4. Two types of waves:
Mechanical
Electromagnetic (will study in next chapter)

5. Mechanical waves require a medium such as air, water, or soil, to transfer the energy from one place to another.
Examples of mechanical waves include waves created by an earthquake, waves created by sound carried through the air, and waves in a pond created by a rock being thrown in.

6. Sound in a Vacuum

7. A wave is created by a vibration being passed from one molecule to another.
The molecules than return to their original position.

8. Vibration Demos
Music Box
Singing Rod with Cup
Speaker with Mirror

9. Electromagnetic waves transfer energy also, but they do not require a medium (vacuum).
Example of an electromagnetic wave is light (can travel in the vacuum of outer space)

10. If a source makes a single disturbance in a wave it is called a single pulse. If the source vibrates repeatedly, it produces a periodic wave.

12. 2 types of mechanical waves include:
Transverse
Longitudinal

13. Transverse vs Longitudinal Demonstration

14. In a transverse wave, the particles in a medium move in a direction that is perpendicular to the direction of the wave motion. Example: a rope being lifted up an down
In a longitudinal wave, the particles in a medium move in the same direction as the wave. Example: a slinky being pushed and pulled back and forth.

15. The highest point on a wave is called the peak or the crest.
The lowest point on a wave is called the trough.

16. The distance from the rope’s equilibrium to the crest is called the amplitude.
The size of the amplitude of a wave determines how much energy the wave transfers.

17. The length of the repeating pattern is called the wavelength.
You measure the wavelength from one crest to the next crest or from one trough to the next trough.

18. Frequency of a wave is the number of waves that occur in a set amount of time.
The Period of a wave is the amount of time it takes for one complete wavelength to pass a point.

19. Ruben’s Flame Demo

20. Frequency equation = 1/Period
f = 1/T
Period equation = 1/frequency
T = 1/f

21. If we have a frequency of 5 Hertz, what is the period?
T = 1/f ; T = 1/5 = .2 s
If we have a period of 1.3 seconds, what is the frequency?
f = 1/T ; f = 1/1.3 = .77 Hertz

22. Not always given the Period but instead given cycles and time.
Frequency = number of cycles / time
f = # of Cycles / t

23. Using a stopwatch, you determine that 3 waves pass a boat every 6 seconds. What is the frequency? What is the period?
f = # of Cycles / t
f = 3 / 6 = .5
T = 1/f ; T = 1 / .5 = 2

25. Speed of a wave equation = wavelength x frequency
v =λf

26. What is the speed of a wave with a wavelength of 2 feet and a frequency of 5 Hz?
v =λf
V = 2 x 5 = 10ft/s

27. A region where the wave is pushed together in a longitudinal wave is called compression.
A region in a longitudinal wave that is pulled apart is called rarefaction.

28. Sound is a longitudinal wave.
The compression and rarefraction of a longitudinal wave is was causes sound.