Exploring Wave Motion: Mechanical vs. Electromagnetic

1. Wave Motion and Sound

2. Part 1:Wave Motion

3. Response Grid Which of the following is an example of a mechanical wave? • Sound • Light • Microwaves • X-rays

4. P4.4A • Describe specific mechanical waves (eg on a demonstration spring, on the ocean) in terms of wavelength, frequency, speed and amplitude.

5. A pulse is a single disturbance. A wave is a series of pulses traveling through space. Wave Motion Pulse Wave: Picture shaking a slinky up and down

6. Wave Motion • Mechanical waves: need a medium (substance) through which to travel • Examples: water waves, slinky waves, sound waves • Electromagnetic waves: do not need a medium through which to travel • Examples: radio waves, microwaves, light, UV rays, x-rays

7. Response Grid Which of the following is an example of a electromagnetic wave? • Sound • Water • X-Rays

8. Response Grid Which of the following is an example of a mechanical wave? • Sound • Light • Microwaves • X-rays

9. Particle Motion • All waves can travel two different ways: • Transverse Wave: particles vibrate perpendicular to direction of traveling wave • Longitudinal Wave: particles vibrate parallel to direction of traveling wave

10. Video • Play Transverse vs. Longitudinal Video

11. Response Grid Which type of wave does not need to travel through a medium? • Electromagnetic • Mechanical

12. Transverse Wave • Crest: top point of wave (green dots) • Trough: bottom point of wave (orange dots) • Amplitude: distance from crest to x-axis • Wavelength: length of one complete “cycle” crest trough

13. Transverse Wave • Frequency: number of “cycles” that pass per second • Can be number of crests, troughs, or wavelengths that pass per second • Symbol: f • Units: 1/seconds or Hertz crest trough

14. Transverse Wave Applet • Wave on a string Applet • Use the applet to change Amplitude and Frequency • Set to oscillate, no end, zero damping

15. Response Grid Which of the following is the wavelength of the wave pictured below? • A • B • C • D A C B D

16. Response Grid Which of the following is the amplitude of the wave pictured below? • A • B • C • D A C B D

17. Response Grid Which of the following is the trough of the wave pictured below? • A • B • C • D A C B D

18. Response Grid Which of the following is the crest of the wave pictured below? • A • B • C • D A C B D

19. P4.4C • Compare and contrast transverse and compression (longitudinal) waves in terms of wavelength, amplitude and frequency.

20. Transverse Wave (Review) • Crest: top point of wave (green dots) • Trough: bottom point of wave (orange dots) • Amplitude: distance from crest to x-axis • Wavelength: length of one complete “cycle” crest trough

21. Compressional Waves • Compression: compressed area of wave • Rarefaction: spread out area of wave • Wavelength: length of one complete “cycle” of wave • measured from compression to compression • Frequency: number of cycles that pass per second Rarefaction

22. Longitudinal vs. Transverse

23. Response Grid Which of the waves below has the larger wavelength? • Wave A • Wave B Wave B Wave A

24. Response Grid Which of the waves below has the larger amplitude? • Wave A • Wave B Wave B Wave A

25. Response Grid Compression is to crest as rarefaction is to • Amplitude • Frequency • Wavelength • Trough • speed

26. Response Grid The number of wave crests per second is called • Wavelength • Frequency • Speed • amplitude

27. P4.4B • Identify everyday examples of transverse and compression (longitudinal waves)

28. Example: Longitudinal Wave • Sound is a longitudinal wave!! • When you speak, you vocal cords vibrate and “bump” the air particles close by. These particles then bump the next particle, etc. • If there were no air particles, there could be no propagation of sound!! • Is there sound in outer space??

29. EM Waves

30. Response Grid Which of the following is NOT a transverse wave? • Light • Water • Rope • sound