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

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 Transverse Compressional/ Compressional/ Longitudinal Longitudinal

5. Transverse Waves TTT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 Sound waves

7. Seismic Waves SSS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 PeriodFrequency 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 Long wavelength = Low frequency Short wavelength = High 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 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 Light waves travel the fastest in empty space and slowest through solids Sound waves travel faster through warmer mediums Sound waves travel faster through warmer mediums

15. Calculating Wave Speed SSSSpeed = wavelength x frequency VVVV = λ x f VVVV = velocity (m/s) λλλλ = wavelength (m) fff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 V = λ x f 12 = (3)(f) 12 = f 3 4 Hz = f

18. Do these on your own 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 For compressional waves it’s the amount of compression in the wave Example: The higher the wave, the more energy (THINK on ocean waves) Example: The higher the wave, the more energy (THINK on ocean waves)

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