Chapter 5 Let Us Entertain You.

1. Chapter 5Let Us Entertain You. Sound and Light

2. How do stringed instruments make notes?

3. How do stringed instruments make notes? • Guitar • Ukelele

4. How do stringed instruments make notes? • Koto • Violin

5. How do stringed instruments make notes? • Piano • Harp

6. A word about pitch: High note = High pitch = High frequency Low note = Low pitch = Low frequency

7. A vibrating string: • What affects the frequency of vibration?

8. Frequency is…… • ______________related to the ___________ of the tension on the string • ______________related to the ___________ of the length of the string • ______________related to the ___________ of the mass of the string

9. Frequency is…… • ____Directly___ related to the _square root_ of the tension on the string • ___Inversely___ related to the _square root_ of the length of the string • ___Inversely___related to the _square root_ of the mass of the string

10. Frequency is…. f= T 4mL

11. Waves: • Carry energy (Greater amplitudemore energy) • Have a velocity, wavelength, frequency and amplitude (Frequency and wavelength are inversely related) • Velocity depends on the medium • Interfere (add up) • Can be transverse (↕) or longitudinal (↔)

12. The wave equation: Velocity = frequency x wavelength v = f l (m/s) = (/s) x (m) (frequency and wavelength are inversely related)

13. Calculate: • Waves on water have a wavelength of 2.0 m, and a frequency of 3 Hz (3 waves / second). What is their speed? • A vibrating guitar string has a frequency of 512 Hz, carrying a wave that moves at 320 m/s. What is its wavelength? • What is the frequency of a radio wave that travels at 3.00 x 10 8 m/s and has a wavelength of 3.134 m?

15. Wave motion  • Wave motion 

16. Motion of medium • Motion of medium

17. What is the wavelength in each case

18. Woodwinds. • The resonance of sound in an open tube: • Please notice the antinodes at the open ends.

19. Woodwinds. • What is the length of the entire wave?

20. Woodwinds. • What is the length of the entire wave? • The tube holds half a wave, so l=2L

21. Other resonance modes: What is the wavelength in each case?

22. In a tube of air, the length of the tube is…

23. If one end is closed: • There is a node at the closed end, and an antinode at the open end.

24. If one end is closed: • There is a node at the closed end, and an antinode at the open end. • What is the length of the wave?

25. If one end is closed: • There is a node at the closed end, and an antinode at the open end. • One-fourth of the wave fits into the tube, so l=4L.

26. Other resonance modes: What is the wavelength in each case?

28. HW p 526 • 1) (Pretty good) • Similar: vibrations make sound, frequency and wavelengths • Different: String vibrating makes air vibrate vs air itself vibrates

29. HW p 526 • 2) a. Did you draw them (3 or 4) full-sized? • b.

30. HW p 526 • 2) b. (cont’d) • c) longest wavelenths=lowest frequencies

31. HW p 526 • answers vary (2.4 m normally—19.5 m record) b. c. L of pipe= ¼ wavelength • (wavelength=4 x L of pipe) • d freq and wavelength are inversely related.

32. HW p 526 4) L of pipe= ¼ wavelength • (wavelength=4 x L of pipe) • f=v/l • Which is higher? How much higher freq.? f=v/l, freqand wavelength are inversely related. 6) t=d/v

33. Apply the wave equation: • A wave has a frequency of 58 Hz and a speed of 31 m/s. What is the wavelength of this wave? • A periodic transverse wave is established on a string such that there are exactly two cycles on a 3.0-m section of the string. The crests move at 20 m/s. What is the frequency of the wave? • A 4-m long string, clamped at both ends, vibrates at 200 Hz. If the string resonates in six segments, what is the speed of transverse waves on the string? • Four standing wave segments, or loops, are observed on a string fixed at both ends as it vibrates at a frequency of 140 Hz. What is the fundamental frequency of the string? • Vibrations with frequency 600 Hz are established on a 1.33-m length of string that is clamped at both ends. The speed of waves on the string is 400 m/s. How many waves are on the string?

34. Light • Light is a transverse wave (an electromagnetic wave) • Light travels in a straight line

35. Light • A shadow falls where light is blocked • No shadow • Shadow • No shadow

36. Light • A shadow falls where light is blocked…BUT! • No shadow • Shadow • No shadow

37. Light • A shadow falls where light is blocked…BUT…a real light source is not a single point.

38. Light • A shadow falls where light is blocked…BUT…a real light source is not a single point. • Shadow from the right side of the bulb

39. Light • A shadow falls where light is blocked…BUT…a real light source is not a single point. • Shadow from the left side of the bulb

40. Light • A shadow falls where light is blocked…BUT…a real light source is not a single point. • Overlapping shadows (umbra)

41. Light • A shadow falls where light is blocked…BUT…a real light source is not a single point. • Non-overlapping shadow (penumbra) • Non-overlapping shadow (penumbra)

42. Light • A shadow falls where light is blocked…BUT…a real light source is not a single point. • Light from both sides (no shadow) • Light from both sides (no shadow)

43. Umbra and Penumbra

44. Umbra and Penumbra

45. Tracing Rays.

48. di do

49. di do

50. di=doThe image is directly behind the mirror at the same distance the object is in front of the mirror di do