2. What are waves? Waves = a transfer of energy from one place to another Ex. = a water wave is a disturbance at the surface of the water. Ex. = a seismic wave is a moves through through the soil of earth

3. Can waves provide energy? Both of the previous waves can transfer their energy Water waves can move a boat up and down – this requires work (energy) Seismic waves can move a building back and forth and up and down

4. What about sound waves? Sounds waves transfer energy with air pressure The sound travels outward in all directions from the source When it reaches your ear, it does work by moving your ear drum

5. Mechanical waves Everything we mentioned are described as mechanical waves These require a medium, such as water, air, even a rope or spring

6. Wave terms Wave pulse – produced if a source makes a single disturbance (like a bang) Period wave – if the source vibrates repeatedly, like a guitar string

7. Transverse wave Particles in the medium, like a rope, move up and down, but the wave moves back and forth.

8. Longitudinal wave Particles move back and forth as well as the wave, like in a slinky spring

9. Peak – each of the highest points of a wave Trough – each of the lowest points of a wave Amplitude – the distance from peak to trough divided by 2

10. Wavelength The wavelength is the length of the repeating pattern Could be from peak to peak

11. Frequency Frequency is number of waves that pass a certain point per unit of time We call this Hertz (Hz)

12. Period of wave The period is the time it takes just one wavelength to pass a point

13. Wave speed = how fast it moves Speed will affect frequency Watch this:

14. Calculating wavelength, Frenquency & Wave Speed f = 1/T where T is the period or time for 1 wave Remember speed = distance / time –What is our distance for waves? –What is our time? Wave speed = wavelength/period –V = / T we can substitute in f for 1/T –To get:v = f *

15. Calculating wavelength, Frenquency & Wave Speed Example – The string of a piano that produces the note middle C vibrates with a frequency of 264 Hz. If the sound waves produced by this string have a wavelength in air of 1.30m, what is the speed of sound in air?