1. Waves Transferring Energy

2. Waves: traveling disturbance that carries energy from one place to another Waves travel through water, but they do not carry the water (or the duck) with them.

3. What causes waves? Vibration: repeated motion starting waves; how waves get their energy

4. Medium Material through which waves travel

5. Mechanical Waves Must have a medium to travel –Examples: ocean waves, sound waves Bell jar example

6. Electromagnetic waves Need no medium to travel –Heat waves (radiation) –Light waves

7. Transverse waves: move the medium at right angles to the direction in which the waves travel vibration Direction of travel

8. Longitudinal: waves move the medium parallel to the direction in which the waves travel.

9. Sound Waves Direction of wave travel Sound waves are longitudinal waves

10. Wavelength The distance between a given point on a wave to the same point on the next wave. Most commonly measured from the center of one crest to the center of the next crest.

11. wavelength crest trough normal amplitude

12. Amplitude Measured from the crest to the wave normal (wave “at rest”). Amplitude is the “power” of the wave

13. wavelength crest trough normal amplitude

14. Frequency The number of waves that pass a certain point in one second. Besides cycles per second, many times frequency is measured in Hertz (Hz). One Hertz is equal to one cycle per second

15. Which wave has the longer wavelength? Which wave has the higher frequency?

16. Which wave has the longer wavelength? Which wave has the higher frequency?

17. Wavelength and frequency have an inverse relationship. As wavelength increases, frequency decreases. Brainpop on Waves

18. Speed of Waves Velocity = frequency x wavelength v = f λ v = velocity f = frequency λ = wavelength

19. Speed of waves practice A middle C note has a wavelength of 1.34 meters. Its frequency is 256 Hz. What is the speed of this sound? Formula: Substitutions: Answer:

20. The approximate outdoor temperature can be calculated by the number of times a cricket chirps per minute. Sound travels at the same speed (343 m/s) at sea level under the same atmospheric conditions (humidity, temperature, etc.). If a cricket’s chirp has a frequency of 180 Hertz, what is the wavelength of the sound? Formula: velocity = frequency x wavelength Substitutions: Answer: