1. The Nature and Properties of Waves
Section 11.1 & 11.2

2. SC Standards Covered
Standard PS-7.1 Illustrate ways that the energy of waves is transferred by interaction with matter (including transverse and longitudinal/compressional waves).
Standard PS-7.2 Compare the nature and properties of transverse and compressional mechanical waves
Standard PS-7.3 Summarize characteristics of waves (including displacement, frequency, period, amplitude, wavelength, and velocity as well as the relationships among these characteristics).\
Standard PS-7.4 Use the formulas v = fλ and v = d/t to solve problems related to the velocity of waves.

3. What’s in a Wave?
Wave – a rhythmic disturbance that transfers energy through matter or space
Carries energy without transporting matter from place to place

4. Mechanical Waves
medium – solid, liquid, or gas that a wave travels through
Two types of mechanical waves:
Transverse
Compressional/
Longitudinal

5. Transverse Waves
Transverse waves – matter moves in the medium back and forth at right angles to the direction that the wave is traveling
Light waves & water waves

6. Compressional Waves
Compressional waves – matter in the medium moves back and forth in the same direction that the wave travels
Sound waves

7. Seismic Waves
Seismic waves – combination of transverse and compressional waves which carry energy along and through Earth

8. The Parts of a Wave Crest – the highest points of a wave
Trough – the lowest points of a wave

9. Compression – place in compressional wave where the particles are pushed together
Rarefaction – place in compressional wave where the particles are spread apart

10. Wavelength
Wavelength – the distance between one point on a wave and the nearest point just like it

11. Frequency and Period
Frequency – the number of waves that pass a given point each second
Measured in Hertz = 1/sec
Period: The amount of time it takes one wavelength to pass a point

12. Period and frequency relationship
T = period
f = frequency
Period Frequency
T= 1/f f = 1/T
One hertz is equal to one peak (or cycle) per second. 1/sec

13. Frequency and Wavelength
Frequency and wavelength are inversely related
Long wavelength = Low frequency
Short wavelength = High Frequency

14. Wave Speed
The speed of a wave depends on the properties of the medium it is traveling through
In general sound waves travel the fastest through solids then liquids then gases
Light waves travel the fastest in empty space and slowest through solids
Sound waves travel faster through warmer mediums

15. Calculating Wave Speed
Speed = wavelength x frequency
V = λ x f
V = velocity (m/s)
λ = wavelength (m)
f = frequency (Hz; 1/sec)

16. Example #1
What is the speed of a wave with a wavelength of 2m and a frequency of 3 Hz?
V = λ x f
V = (2)(3)
V = 6 m/s

17. Example #2
A wave is traveling at a speed of 12 m/s and its wavelength is 3m. Calculate the wave’s frequency.
V = λ x f
12 = (3)(f)
12 = f 3
4 Hz = f

18. Do these on your own 
A tuning fork has a frequency of 280 Hertz and the wavelength of the sound produced is 1.5 meters. Calculate the velocity of the wave.
A wave is moving toward shore with a velocity of 5.0 m/s. If its frequency is 2.5 hertz, what is its wavelength?

19. Amplitude and Energy
Amplitude – the energy carried by a wave or how high the wave is; related to the amount of energy
For compressional waves it’s the amount of compression in the wave
Example: The higher the wave, the more energy (THINK on ocean waves)

20. For transverse waves it’s the height of the wave