1. AIM: WAVES and Optics
WRITE NOW: What is a wave? What is a medium?

2. WAVES
A wave is a disturbance or variation that travels through a medium.
A medium is the substance or material that carries the wave.
Note that a wave does not permanently transport matter. The matter will return to its initial position.

3. Energy transport phenomenon!
Energy is transferred through a wave, but there is no net motion of the medium!

4. WAVES
Longitudinal waves
Transverse waves

5. ANATOMY OF A WAVE
DEFINE: Amplitude, Wavelength

6. WAVES
Period: The time for a particle on a medium to make one complete cycle.
Frequency: The number of complete cycles in a medium in a given amount of time
Hertz: (Hz) 1 Hertz is equal to one cycle/second
Define: Displacement, Amplitude, Frequency, Period, Wavelength, Wave Speed (derive!)

7. Frequency and Period T = 1/f f = 1/T
Rachel accompanies her father to the park for an afternoon of fun. While there, she hops on the swing and begins a motion characterized by a complete back-and-forth cycle every 5.0 seconds. What is the frequency and period of her motion?

8. Frequency and Period
A hummingbird can flap its wings 3000 times in one minute. Calculate the frequency and period of this motion.

9. AIM: Calculating the Velocity of a Wave.
WRITE NOW: Justin Bieber stands 170 meters away from a steep canyon wall. He shouts “Baby, Baby! Help me!” and hears the echo of his voice one second later. What is the speed of the wave?

10. Frequency, Period and Wave Speed
Lady Gaga and Lily Allen are at a dock on a lake. They are counting the waves going by.
In 45 seconds, 15 waves go by. What is the frequency of these waves? When is the period?
B) If each wave is 0.8m long*, what is the velocity of the wave?
*Lady Gaga and Lily Allen are both excellent at math.

11. Wave Speed: The distance traveled by a given point on the wave (such as a crest) in a given interval of time.
A wave travelling on a string has a wavelength of 0.10 m and a frequency of 7 Hz.  Calculate the speed of the wave.

12. The Wave Equation
Since period and frequency are inversely related: Speed = Wavelength • Frequency

13. Amplitude of Waves High Amplitude= High Energy
Low Amplitude= Low Energy

14. Waves
1. Frank and Beans stand 8 meters apart and demonstrate the motion of a transverse wave on a slinky. The wave can be described as having a vertical distance of 32 cm from a trough to a crest, a frequency of 2.4 Hz, and a horizontal distance of 48 cm from a crest to the nearest trough. Determine the amplitude, period, and wavelength of such a wave.
Amplitude: 16 cm Period: T=1/f T=1/2.4 Hz T= 0.4 seconds. Wavelength: 48 cm x 2= 96 cm

15. AIM: WAVE BOUNDARIES
WRITE NOW: What do the following things have in common?

16. WAVE BOUNDARIES
And these?

17. WAVE BOUNDARIES Simple Harmonic Motion
Unless acted on by an unbalanced force, this particle will move like this forever!

18. WAVE BOUNDARIES
Dampened Harmonic Motion

19. WAVES

20. The Electromagnetic Spectrum

21. WAVE Boundaries Describe the motion of both types of waves.
Fixed Boundary
Free Boundary
Describe the motion of both types of waves.

22. WAVE Fronts
Wave fronts/rays

23. WAVE INTERACTIONS
Reflection

24. WAVE INTERACTIONS
Reflection

25. WAVES
Reflection

26. WAVE INTERACTIONS
Diffraction

27. WAVE INTERACTIONS
Diffraction

28. WAVES
Diffraction

29. AIM: Snell’s Law
WRITE NOW: How does the frequency and wavelength of a wave change as it passes through an opening within a border?

30. WAVE INTERACTIONS
Refraction

31. WAVE INTERACTIONS
Refraction

32. WAVES
Refraction

33. WAVE INTERACTIONS Specular Diffuse
Man, I LOVE RAINBOWS!! Just LOVE ‘EM!!!!
Specular
Diffuse

34. WAVE INTERACTIONS Refraction
-----short wavelength/high frequency waves bend more than long wavelength/low frequency waves
So what does this have to do with rainbows? The flying horse wants to know!!!!!!

35. Index of Refraction
Ratio of light speed in a vacuum to light speed in a particular material.
The more dense the material, the greater the refraction (thus the greater index of refraction.)

36. WAVES
v1 sin θ1
v2 sin θ2

37. WAVES: Snell’s Law n1= index of refraction for the first medium.
n2= index of refraction for the second medium
Θ1= angle of incidence
Θ2= angle of refraction

38. And now for something completely different…

39. What is Happening Here?

40. The Doppler Effect
WRITE NOW: What’s the Doppler Effect?

41. But first, how do we describe sound?
Tone: A sound that you hear with regular, evenly spaced waves.
Pitch: Refers to how far away those waves are spaced (sound familiar?). Close waves=High Pitch; Distant waves=Low Pitch

43. The Doppler Effect
Sound moves towards you, waves compress. Wavelengths decrease and frequency increases.
Sound moves away, waves spread out. Wavelengths increase and frequency decreases.

44. WAVES

45. Doppler Effect Formula

46. Doppler Effect Formula
An ambulance is traveling at a velocity of 80 km/hr. The siren’s frequency is 440 Hz. What is the perceived frequency of the approaching source? What is the perceived frequency of the receding source?

47. Doppler Effect Formula
First, convert the velocity to meters/second.
Identify your variables (what you are given)
fsource= 440 Hz - fobserved= ?
Vsource= m/s
Vsound= m/s
80 km
1000 m
1 hr
1 min
1 km
60 min
60 sec

48. Doppler Effect Formula
Write your formulas.
Receding Source:
fobserved= ( vsound/vsound+ vsource)fsource
Approaching Source:
fobserved= (vsound/vsound – vsource)fsource

49. Doppler Effect Formula
Show your work.
Receding Source:
fobserved = (341m/s ÷ 341 m/s m/s)440Hz
413.1 Hz
Approaching Source:
fobserved= (341 m/s ÷ 341m/s – 22.2 m/s) 440 Hz
470.6 Hz

50. Explains how we know the universe is expanding!
Red Shift/Blue Shift
Explains how we know the universe is expanding!

51. Red Shift/Blue Shift

52. The Doppler Effect

53. Waves

54. WaveS

55. Waves