Waves, Sound, and EM Spectrum

1. Waves, Sound, and EM Spectrum

2. Waves, EM Spectrum and Sound Describe how energy is transferred through sound waves and how pitch and loudness are related to wave properties of frequency and amplitude.

3. An Introduction to Waves

4. Waves: repeated disturbances in a medium (substance) that transfers energy through it Medium: the material the wave travels through (air, water, etc) Water Tuning fork

5. 2 Main Types of Waves: Transverse wave: The matter moves upand down as the wave travels horizontally Compressional (Longitudinal) wave: Matter and wave move horizontally Which is which? 

6. TRAVIS the (transverse wave) Caterpillar

7. Transverse Waves

8. Draw this picture of a Transverse Wave:

9. Fancy words for your wave: Crest: highest point Trough: lowest point Wavelength (λ): length from crest to crest (or trough to trough)

10. Frequency (f): number of wavelengths that pass a point each second A.k.a. pitch (1 Hertz = 1 wavelength per second) Period: amount of time it takes one wavelength to pass a point Amplitude: measure from equilibrium position to top of crest or bottom of trough. A.k.a. loudness

11. How do you measure wavelength and frequency?

12. How do you measure wavelength and frequency?

13. WORK ON: Waves WS

14. Compressional Waves

15. Draw this picture of a Compressional Wave:

16. (More terms? Yaaaaaay!!!) Compression and Rarefaction Compression Rarefaction

17. Wavelength (λ): From compression to compression (or expansion to expansion) Frequency (f): number of wavelengths that pass a point each second Period: amount of time it takes one wavelength to pass a point Amplitude: more compressed it is, the more amplitude (loudness) it has

18. Amplitude in Transverse vs Compression Waves

19. Where is the crest? Trough?

20. What pattern do you notice between wavelength and frequency? As wavelength increases, frequency ______ As frequency increases, wavelength ______

21. What is wavelength?What is frequency? https://www.youtube.com/watch?v=Xu6hbS2TLSw

22. Relationship btw Frequency and Wavelength (watch the volume) https://www.youtube.com/watch?v=HVmt1DQWalQ

23. Think of your own comparison: A transverse wave is like ___________ A compression wave is like ___________ Using a slinky, how can you show a transverse wave and a compressional wave?

24. Pitch and Loudness

25. Sound Intensity: more energy = more intensity more distance from source = less intensity Discuss: Which of the above waves has high intensity?

26. Loudness (decibel or dB): how the ear and brain understands sound intensity.

27. How the brain interprets sound waves

28. http://www.educationscotland.gov.uk/resources/s/sound/amplitude.asphttp://www.educationscotland.gov.uk/resources/s/sound/amplitude.asp

29. Pitch: how the ear and brain understand frequency (or wavelength) (high pitch of a mosquito vs low pitch of a tuba) Humans can hear sounds from 20 Hz to 20,000 Hz. (Dogs: up to 35,000Hz……Bats: up to 100,000 Hz) What is the relationship between pitch and frequency?

30. Pipe Cleaner Wave Models

31. Create a Wave… Table 1 & 3: Transverse, High freq, low amp Table 4 &6: Compressional, high freq, high amp Table 5 &7: Transverse, low freq, low amp Table 2 & 8: Compressional, low freq, high amp

32. Line up by… • Frequency • Amplitude • Loudness • Pitch 4 corners: soft sound, loud sound, high pitch, low pitch

33. Waves Lab #1 Slinkies/Snakies

34. Slinky and Snaky (helical spring) used to ask many questions about waves (4 minutes): http://www.youtube.com/watch?v=zyqCgtvMwfw

35. Sound

36. Sound waves = Compressional Waves (a.k.a. Longitudinal Waves) in the medium of air Compression Compression Compression Compression

37. JUST THINK:What would sound waves “look” like? (3 min) http://www.youtube.com/watch?v=_vYYqRVi8vY What happens in soft sounds? What happens in loud sounds? Does air itself travel when a sound wave passes through it? Higher frequency means _______ pitch sound.

39. Discuss: Which of the above are waves? Which of the above are sound waves? Which of the above waves are heard as LOUDER in your ear? Which of the above waves has a higher pitch?

40. Doppler Effect and Red Shift

41. Doppler Effect: a change in pitch that is due to a moving source Moving towards you increases frequency (pitch) Moving away from you decreases frequency (pitch)

42. WHAT DOES THIS SOUND LIKE AS IT PASSES YOU?? HOW DOES THE SOUND CHANGE AS IT PASSES YOU?

43. When is the motorcycle pitch high? When is the motorcycle pitch low? What does a high pitch wavelength look like? What does a low pitch wavelength look like?

44. How can a tuning fork show that sound compresses air? How can a tuning fork be used to show the Doppler Effect?

45. Car moving to the right

46. Tuning Fork  Evidence: How does the action of a tuning fork that is struck and placed in water show evidence that sound pushes air and travels in waves? How does a tuning fork that is rapidly moved (closer-further-closer-further) from your ear show the Doppler Effect?

47. Redshift • the Doppler Effect on light emitted from moving planets!

48. When planets move away from you, the wavelength gets longer and more RED!!

49. When planets move towards you, the wavelength gets shorter and more BLUE!!

50. Questions for the Doppler Video • How many sounds does a tuning fork make? • Why did the sound change as he moved it? • How many sounds does the “football” make? • Why did the sound change as he moved it?