1. Introduction to Waves
Resources: The Physics Classroom, Daniel A. Russell

2. What is a Wave? Wave: motion of a disturbance
Disturbance creates waves that travel away from the source of the disturbance
Waves transport energy, not matter.
Mechanical waves require a medium: the elastic, deformable matter through which disturbance travels
Electromagnetic waves don’t require a medium

3. Waves Transport Energy not Matter
Long
Tall

4. Types of Waves Pulse Wave: source is a non- periodic disturbance
Periodic Wave: source is a periodic oscillation
If source is Simple harmonic oscillation (SHO), wave form is sine wave
Common forms:
Transverse
Longitudinal

5. Transverse Waves Medium moves perpendicular to direction wave travels
Examples: Light, strings, seismic s-waves, water waves

6. Transverse Wave

7. Medium moves parallel (in line) to direction wave travels
Longitudinal Wave
Medium moves parallel (in line) to direction wave travels

8. Longitudinal Waves (cont.)
Compression: where wave fronts are closer together than in undisturbed medium
Rarefaction: where they are farther apart than in undisturbed medium

9. Longitudinal Wave

10. Other Waves

11. Quiz time!
Not really, just some questions to check for your level of mastery.

12. Waves transport matter from one location to another without transporting energy.
True
False

13. Which diagram - A, B, C, or D
represents the appropriate
hand movements and patterns
for a longitudinal wave?

14. If a longitudinal wave is created in a medium that extends horizontally from left to right, then the particles of the medium will vibrate in a ____ direction.
Horizontal
Vertical
diagonal (both horizontal and vertical)
circular
none of these

15. Back to notes: Wave Parts
The following words are used to describe waves:
Amplitude
Wave length
Frequency
Period
Speed

16. Amplitude (A) How “tall” (or “wide”) the wave is
Maximum displacement from the average or equilibrium position
Crests: highs
Troughs: lows
Measured from “crest to rest” or “trough to rest”
Unit of measure: meter

17. Amplitude and Energy

18. Wave Length (λ)
Distance from a point on one wave to the same point on the next wave
Unit of measure
meter
Graph of displacement versus distance is a “snapshot” of the wave at a given time

19. A wave is established in a rope
A wave is established in a rope. The diagram below represents a snapshot of the pattern in the rope at a given instant in time. Several points on the rope are labeled with a letter. Identify the letters of any wave crests. List all that apply in alphabetical order with no spaces or commas between letters.

20. Frequency
Frequency: number of cycles (repetitions) per unit of time (how often wave cycles)
Units
Hz (cycles/second)

21. Frequency (cont.)
The higher frequency wave has more complete cycles in the same amount of time
The upper wave has 2 x the frequency of the bottom. Note that the x-axis has units of time in this graph.
Graph of displacement versus time shows the motion of a given position

22. Period (T)
Period: Time for one complete wave to pass any given point
Unit of measure
seconds
The period and frequency are reciprocals:
T = 1/f
f = 1/T

23. Wave Speed (v)
Wave Speed: How fast a wave transmits energy from one place to another
IMPORTANT: Wave speed depends only on specific properties of the medium)
Constant for a given medium at given conditions
Unit of measure
meter/second
Examples: Speed of wave in string depends on tension and linear density. Speed of wave in fluid depends on bulk modulus and density. Speed of wave in solid depends on elastic modulus and density.

24. Wave speeds vary widely:
Wave Speed (cont.)
Wave speeds vary widely:
Water waves: a few miles per hour
Sound (in air): about 340 m/sec or ft/sec (depends on temperature)
Electromagnetic Waves (such as light) travel about 300,000,000 meters/sec or 186,000 miles/sec

25. A wave is moving through a coiled Slinky™
A wave is moving through a coiled Slinky™. The time for a single coil to complete one full back and forth vibration is known as the _____. a. speed b. period c. amplitude d. frequency

26. A long rope is vibrated on one of its ends in order to produce a wave
A long rope is vibrated on one of its ends in order to produce a wave. A single point on the rope makes 4.0 complete vibrations every second. The quantity 4.0 refers to the _____ of the wave. a. speed b. period c. amplitude d. frequency

27. The wavelength of the wave is equal to _____.C

28. The amplitude of the wave is equal to _____.

29. Compared to the wave in Diagram B, the wave in Diagram A has _____.
the same amplitude by a larger wavelength
a larger amplitude and a smaller wavelength
a smaller amplitude and the same wavelength
the same amplitude and a smaller wavelength

30. Wave Properties (cont.)
Here’s an example transverse wave showing some of the quantities we’ve talked about so far: 1 2 3 4 5
Answer: 2 complete wavelengths are shown
How many complete wavelengths are shown?